Untitled Quiz

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

How do bacteria and unicellular eukaryotes respond to signals?

Bacteria and unicellular eukaryotes respond to environmental signals and to signaling molecules secreted by other cells for mating and other communication.

In multicellular organisms, cell-cell communication is not very sophisticated.

False

What initiates a series of reactions that regulate all aspects of cell behavior?

Binding of signal molecules to receptors initiates a series of reactions that regulate all aspects of cell behavior.

Many cancers arise from problems in signaling pathways.

True Signup and view all the answers

Much of our understanding of cell signaling comes from the study of healthy cells.

False Signup and view all the answers

Signaling molecules can range in complexity from to .

proteins Signup and view all the answers

Which of the following modes of cell signaling involves direct interaction between neighboring cells?

Direct cell-cell signaling Signup and view all the answers

What type of signaling involves molecules released by one cell acting on neighboring target cells?

Paracrine signaling Signup and view all the answers

What is an example of a paracrine signaling molecule?

Neurotransmitters Signup and view all the answers

What type of signaling involves cells responding to signaling molecules that they themselves produce?

Autocrine signaling Signup and view all the answers

Abnormal autocrine signaling is often associated with cancer.

True Signup and view all the answers

Where can receptors for signaling molecules be located?

Both A and B Signup and view all the answers

What type of molecules do intracellular receptors respond to?

Small hydrophobic molecules that can diffuse across the plasma membrane Signup and view all the answers

What are some examples of molecules that bind to intracellular receptors?

Steroid hormones, thyroid hormone, vitamin D3 and retinoic acid Signup and view all the answers

Steroid hormones are synthesized from cholesterol

True Signup and view all the answers

Which of the following are considered sex steroids?

All of the above Signup and view all the answers

What type of steroid hormones are produced by the adrenal gland?

Corticosteroids Signup and view all the answers

What is an example of a plant steroid hormone?

Brassinosteroids Signup and view all the answers

What is the function of thyroid hormone?

Thyroid hormone is synthesized from tyrosine in the thyroid gland, and it is important in development and metabolism. It plays a crucial role in regulating energy expenditure, growth, and development. Signup and view all the answers

What is the function of Vitamin D3?

Vitamin D3 regulates Ca2+ metabolism and bone growth. It is essential for strong bones, muscle function, and overall immune function. Signup and view all the answers

What is the function of retinoic acid and retinoids?

Retinoic acid and retinoids are synthesized from vitamin A and they are important in vertebrate development, playing a crucial role in embryonic development and regulating various bodily functions. Signup and view all the answers

What is the nuclear receptor superfamily?

The nuclear receptor superfamily consists of receptors for steroid hormones, thyroid hormone, vitamin D3, and retinoic acid. They are transcription factors with domains for ligand binding, DNA binding, and transcriptional activation. The steroid hormones and related molecules directly regulate gene expression. Signup and view all the answers

Ligand binding always activates nuclear receptors.

False Signup and view all the answers

Glucocorticoid receptor is bound to Hsp90 chaperones in the absence of hormone.

True Signup and view all the answers

What is a common cellular response to the binding of glucocorticoids?

Glucocorticoid binding displaces Hsp90 and leads to binding of regulatory DNA sequences, ultimately regulating gene expression. Signup and view all the answers

In the absence of hormone, thyroid hormone receptor is associated with a corepressor complex and represses transcription of target genes.

True Signup and view all the answers

What happens when hormone binds to the thyroid hormone receptor?

Hormone binding results in activation of transcription. Signup and view all the answers

Most ligands responsible for cell-cell signaling bind to intracellular receptors.

False Signup and view all the answers

What is the main function of intracellular signal transduction?

The surface receptors regulate intracellular enzymes, which then transmit signals from the receptor to a series of additional intracellular targets. Signup and view all the answers

The targets of signaling pathways frequently include transcription factors

True Signup and view all the answers

What initiates a chain of intracellular reactions in a signaling pathway?

Ligand binding to a receptor initiates a chain of intracellular reactions, ultimately reaching the nucleus and altering gene expression. Signup and view all the answers

What is the largest family of cell surface receptors?

G protein-coupled receptors Signup and view all the answers

What is the function of G proteins in cell signalling?

G proteins, also known as guanine nucleotide-binding proteins, are involved in transmitting signals from the receptor to various intracellular targets. They play a crucial role in mediating cellular responses to a wide range of stimuli. Signup and view all the answers

How many subunits do G proteins have?

G proteins typically consist of three subunits, designated as alpha (α), beta (β), and gamma (γ). Signup and view all the answers

G proteins are also called heterotrimeric G proteins to distinguish them from other guanine nucleotide-binding proteins.

True Signup and view all the answers

What are some examples of guanine nucleotide-binding proteins?

Examples of guanine nucleotide-binding proteins include G proteins and Ras proteins. These proteins play a role in various cellular processes, including signal transduction and growth control. Signup and view all the answers

How many transmembrane alpha helices do G protein-coupled receptors have?

G protein-coupled receptors have seven transmembrane alpha helices, which provide a scaffold for the protein to span the cell membrane. Signup and view all the answers

What type of cellular change occurs when a ligand binds to a G protein-coupled receptor?

Binding of a ligand to a G protein-coupled receptor induces a conformational change that allows the cytosolic domain to activate a G protein on the inner face of the plasma membrane. Signup and view all the answers

What does the activated G protein do?

The activated G protein dissociates from the receptor and carries the signal to an intracellular target, triggering a cascade of events that ultimately lead to cellular responses. Signup and view all the answers

What is cyclic AMP, and what is its role in cell signalling?

Cyclic AMP (cAMP) is a second messenger that mediates responses to many hormones. It plays a crucial role in signal transduction, facilitating communication within the cell and influencing various cellular processes. Signup and view all the answers

G proteins were discovered during studies of cyclic AMP.

True Signup and view all the answers

A G protein is an intermediary in adenylyl cyclase activation, which synthesizes cAMP.

True Signup and view all the answers

What is the role of the alpha subunit in G protein activity?

The alpha subunit binds guanine, which regulates G protein activity. It can bind to GDP (guanosine diphosphate) or GTP (guanosine triphosphate). The binding of GTP to the alpha subunit activates the G protein, while the binding of GDP inactivates it. Signup and view all the answers

In its inactive state, the alpha subunit of G proteins is bound to GDP in a complex with beta and gamma subunits.

True Signup and view all the answers

What causes the exchange of GTP for GDP in G proteins?

Hormone binding to the receptor causes exchange of GTP for GDP. This activation of the G protein initiates a signaling cascade within the cell. Signup and view all the answers

After GTP replaces GDP in G proteins, the alpha and beta-gamma complex dissociate from the receptor and interact with their targets.

True Signup and view all the answers

The activated G protein then phosphorylates its target proteins.

False Signup and view all the answers

G proteins were discovered during studies of cyclic AMP, which is a second messenger.

True Signup and view all the answers

What does adenylyl cyclase do?

Adenylyl cyclase is an enzyme that synthesizes cAMP from ATP. It is an important target in G protein-coupled signaling pathways, leading to changes in cellular activity. Signup and view all the answers

Cyclic AMP is formed from ATP by adenylyl cyclase and degraded to AMP by cAMP phosphodiesterase.

True Signup and view all the answers

What is protein kinase A?

Protein kinase A (PKA) is an enzyme that is activated by cAMP. It plays a vital role in cellular signaling by phosphorylating other proteins, thereby influencing a wide range of cellular functions, including metabolism, growth, and gene expression. Signup and view all the answers

Protein kinase A is inactive in the absence of cAMP.

True Signup and view all the answers

What are the regulatory subunits of protein kinase A?

Protein kinase A has two regulatory subunits. cAMP binds to these subunits, causing them to dissociate from the catalytic subunits. Signup and view all the answers

What happens when the catalytic subunits of protein kinase A are released by the regulatory subunits?

The free catalytic subunits can then phosphorylate serine on target proteins, triggering changes in protein activity and cellular function. Signup and view all the answers

Epinephrine activates the breakdown of glycogen into glucose in muscle cells.

True Signup and view all the answers

Protein kinases function in isolation

False Signup and view all the answers

What do protein phosphatases do?

Protein phosphatases remove the phosphate groups added by protein kinases, rapidly reversing the phosphorylation process. Signup and view all the answers

Cyclic AMP can also directly regulate ion channels

True Signup and view all the answers

What is the role of cyclic AMP in sensing smells?

Odorant receptors in the olfactory system are G protein-coupled. They stimulate adenylyl cyclase, leading to increased cAMP. cAMP opens sodium channels in the plasma membrane, leading to initiation of a nerve impulse, allowing the brain to interpret smell signals. Signup and view all the answers

What are tyrosine kinases?

Tyrosine kinases are a family of enzymes that phosphorylate their substrates on tyrosine residues. They play a critical role in various cellular signaling pathways, including those responsible for growth, development, and cell division. Signup and view all the answers

What are the two types of tyrosine kinases?

The two types of tyrosine kinases are receptor tyrosine kinases, which reside on the cell surface, and non-receptor tyrosine kinases, which are located within the cytoplasm. Signup and view all the answers

The human genome encodes 58 receptor tyrosine kinases.

True Signup and view all the answers

All receptor tyrosine kinases have an N-terminal extracellular ligand-binding domain, one transmembrane alpha helix, and a cytosolic C-terminal domain with protein-tyrosine kinase activity.

True Signup and view all the answers

What happens when ligands bind to the extracellular domains of receptor tyrosine kinases?

Binding of ligands to the extracellular domains of receptor tyrosine kinases activates the cytosolic kinase domains. This is often accompanied by dimerization of the receptor, increasing its signaling activity. Signup and view all the answers

What is autophosphorylation?

Autophosphorylation is a process where a protein phosphorylates itself, often occurring in tyrosine kinases. In receptor tyrosine kinases, this typically involves cross-phosphorylation between two subunits of the dimerized receptor, leading to enhanced signaling activity. Signup and view all the answers

Autophosphorylation of tyrosine in the catalytic domain can increase protein kinase activity.

True Signup and view all the answers

Autophosphorylation of tyrosine residues outside of the catalytic domain does not create binding sites for other proteins

False Signup and view all the answers

What are SH2 domains?

SH2 domains are protein domains found in signaling proteins. They bind to specific phosphotyrosine-containing peptides of the activated receptors. Signup and view all the answers

Where were SH2 domains first discovered?

SH2 domains were first recognized in tyrosine kinases related to Src, a protein involved in cellular signaling and cancer development. Signup and view all the answers

Nonreceptor tyrosine kinases do not stimulate intracellular tyrosine kinases.

False Signup and view all the answers

What does the cytokine receptor superfamily contain?

The cytokine receptor superfamily contains receptors for most cytokines and some polypeptide hormones. These receptors are involved in a wide range of signaling pathways, primarily regulating immune responses and cell development. Signup and view all the answers

The structure of cytokine receptors is identical to receptor tyrosine kinases.

False Signup and view all the answers

What does ligand binding induce in cytokine receptors?

Ligand binding to cytokine receptors induces dimerization of the receptors and cross-phosphorylation of associated nonreceptor tyrosine kinases. These events create a signaling complex that activates downstream pathways, leading to changes in cellular activity. Signup and view all the answers

Activated kinases phosphorylate the receptor, providing phosphotyrosine-binding sites for recruitment of downstream signaling molecules with SH2 domains. This helps propagate the signal.

True Signup and view all the answers

The downstream signaling molecules are not involved in the propagation of the signal.

False Signup and view all the answers

The nonreceptor tyrosine kinases do not involve intracellular tyrosine kinases.

False Signup and view all the answers

The cytokine receptor superfamily is a large family which includes receptors for most cytokines and some hormones.

True Signup and view all the answers

Study Notes

Cell Signaling

Cells receive and respond to signals from their environment.
Bacteria and unicellular eukaryotes respond to environmental signals and signals from other cells.
Multicellular organisms have sophisticated cell-cell communication to meet the needs of the entire organism.
Signaling molecules are secreted or expressed on one cell surface to bind to receptors on another cell.
Binding of signal molecules to receptors starts a chain of reactions affecting cell behavior.
Many cancers arise from problems in signaling pathways that control normal cell proliferation.

Signaling Molecules and Their Receptors

Signaling molecules range from simple gases to proteins.
Some molecules carry signals over long distances, while some act locally.
Some molecules cross the plasma membrane to bind to intracellular receptors, others bind to cell surface receptors.

Modes of Cell Signaling

Direct cell-cell signaling: Direct interaction of a cell with its neighbor (e.g., via integrins and cadherins).
Signaling by secreted molecules: Three categories based on the distance over which signals are transmitted.

Endocrine Signaling

Signaling molecules (hormones) are secreted by specialized endocrine cells and carried through the circulatory system to distant target cells.
Example: Estrogen.

Paracrine Signaling

Molecules released by one cell act on neighboring target cells.
Example: Neurotransmitters.

Autocrine Signaling

Cells respond to signaling molecules they themselves produce.
Example: T lymphocytes respond to antigens by making growth factors that drive their proliferation, amplifying the immune response.
Abnormal autocrine signaling often contributes to cancer.

Receptors

Receptors may be located on the cell surface or inside the cell.
Intracellular receptors respond to small hydrophobic molecules that can diffuse across the plasma membrane.
- Examples: steroid hormones, thyroid hormone, vitamin D3, and retinoic acid.
Steroid hormones are synthesized from cholesterol.
- Testosterone, estrogen, and progesterone are sex steroids produced by the gonads.

Corticosteroids

Glucocorticoids from the adrenal gland stimulate glucose production.
Mineralocorticoids from the adrenal gland act on the kidneys to regulate salt and water balance.
Ecdysone is an insect hormone that triggers larval metamorphosis to adults.
Brassinosteroids are plant steroid hormones that control processes, including cell growth and differentiation.
Thyroid hormone is synthesized from tyrosine in the thyroid gland and is pivotal for development and metabolism.
Vitamin D3 regulates calcium metabolism and bone growth.
Retinoic acid and retinoids are synthesized from vitamin A and crucial for vertebrate development.
Receptors for these molecules belong to the nuclear receptor superfamily—transcription factors with domains for ligand binding, DNA binding, and transcriptional activation.
Steroid hormones directly regulate gene expression.
Ligand binding affects receptor activity differently depending on the receptor.

Ligand Binding

Glucocorticoid receptors are bound to Hsp90 chaperones in the absence of hormone.
Glucocorticoid binding displaces Hsp90, leading to binding of regulatory DNA sequences.
Hormone binding can alter the activity of some receptors, for example, thyroid hormone receptors bind with corepressor complexes to repress transcription in the absence of hormones. Hormone binding leads to activation of transcription.

Nitric Oxide (NO)

NO is a gas, crossing the plasma membrane to alter enzyme activity.
NO is a paracrine signaling molecule in nervous, immune, and circulatory systems.
Actions are local due to instability (half-life of a few seconds).
The main target of NO is guanylyl cyclase, which stimulates cyclic GMP (cGMP) synthesis—a second messenger.
NO signals dilation of blood vessels. It diffuses to smooth muscle cells, stimulating cGMP production and inducing muscle relaxation and blood vessel dilation.
Carbon monoxide (CO) is another signaling molecule in the nervous system. It acts similarly to NO, as a neurotransmitter and mediator of blood vessel dilation.

Neurotransmitters

Neurotransmitters carry signals between neurons or from neurons to other cells.
Released when an action potential arrives at the end of a neuron.
Neurotransmitters diffuse across the synaptic cleft and bind to receptors on the target cell surface.
Neurotransmitters (hydrophilic) can't cross plasma membranes and bind to cell surface receptors.
The receptors are often ligand-gated ion channels, opening when neurotransmitters bind.
Neurotransmitter receptors can also involve enzyme-coupled receptors or G proteins.

Peptide Signaling Molecules

Peptide signaling molecules (peptide hormones, neuropeptides, and growth factors) can't cross plasma membranes, acting by binding to cell surface receptors.
Abnormalities in growth factor signaling cause various diseases, including cancers.
Peptide hormones include insulin, glucagon, and pituitary hormones (e.g., growth hormone, follicle-stimulating hormone, prolactin).
Neuropeptides are secreted by neurons; enkephalins and endorphins act as neurotransmitters and analgesics similar to morphine effects.
Nerve growth factor (NGF) is a member of the neurotrophin family, regulating neuron development and survival.
Epidermal growth factor (EGF) stimulates cell proliferation and is a prototype for growth factors.
Platelet-derived growth factor (PDGF) is stored in blood platelets, released during blood clotting, and stimulates fibroblast proliferation, contributing to tissue regrowth.
Cytokines regulate blood cell development and lymphocyte activities in immune responses.
Membrane-anchored growth factors remain with the plasma membrane and function in direct cell-cell interactions.

Plant Hormones

Gibberellins: stem elongation.
Auxins: cell elongation.
Ethylene: fruit ripening.
Cytokinins: cell division.
Abscisic acid: onset of dormancy.

G Proteins and Cyclic AMP Signaling

Most ligands for cell-cell signaling bind to target cell surface receptors.
Intracellular signal transduction: Surface receptors regulate intracellular enzymes transmitting signals from the receptor to other intracellular targets.
Targets of signaling pathways frequently include transcription factors.
Ligand binding to receptors triggers a chain of intracellular reactions to reach the nucleus, altering gene expression.
G protein-coupled receptors are the largest family of cell surface receptors transmitting signals via guanine nucleotide-binding proteins (G proteins).
G proteins have three subunits (α, β, and γ).
Receptors have seven membrane-spanning α helices.
Ligand binding induces a conformational change in the receptor, activating a G protein on the inner face of the plasma membrane.
The activated G protein dissociates, carrying the signal to an intracellular target.
G proteins were discovered during studies of cyclic AMP (cAMP) a second messenger mediating hormone responses.
The α subunit binds guanine, regulating G protein activity. In its inactive state, α is bound to GDP. Hormone binding triggers exchange of GTP for GDP; the α and βγ complex dissociate and interact with their targets.
cAMP is formed from ATP by adenylyl cyclase and is degraded to AMP by cAMP phosphodiesterase.
Effects of cAMP are mediated by cAMP-dependent protein kinase (protein kinase A). Inactive protein kinase A has two regulatory and two catalytic subunits. cAMP binding to regulatory subunits causes dissociation. The free catalytic subunits phosphorylate serine on target proteins.
In glycogen metabolism, protein kinase A phosphorylates two enzymes:
- Phosphorylase kinase is activated, further activating glycogen phosphorylase for glycogen breakdown.
- Glycogen synthase is inactivated, blocking glycogen synthesis.
Signal amplification: Binding of a hormone molecule activates many intracellular target enzymes.
G_s stimulates adenylyl cyclase, catalyzing cAMP synthesis.
Protein kinase A phosphorylates many molecules of phosphorylase kinase, which phosphorylates many molecules of glycogen phosphorylase.
In many animal cells, increases in cAMP activate transcription of genes with regulatory sequences called cAMP response elements (CREs). The free catalytic subunit of protein kinase A goes to the nucleus and phosphorylates the transcription factor CREB (CRE-binding protein).
Phosphorylation of CREB recruits coactivators, expressing cAMP-inducible genes, which play roles in cell behavior.
Protein kinases don't function alone. Protein phosphatases reverse protein phosphorylation, ending receptor-initiated kinase responses.
cAMP can directly regulate ion channels in some animal cells; odorant receptors are G protein-coupled, stimulating adenylyl cyclase, and leading to an increase in cAMP. cAMP opens Na+ channels to initiate a nerve impulse.

###Tyrosine Kinases and Signaling by MAP Kinase, PI 3-Kinase, and Phospholipase C/Calcium Pathways

Other cell surface receptors are directly linked to intracellular enzymes, including a large family of tyrosine kinases.
Receptor tyrosine kinases phosphorylate their substrates on tyrosine residues.
Receptor tyrosine kinases have an N-terminal extracellular ligand-binding domain, a transmembrane α helix, and a cytosolic C-terminal domain for protein tyrosine kinase activity.
Binding of ligands (growth factors) to extracellular domains activates cytosolic kinase domains, resulting in phosphorylation of both receptors and intracellular target proteins.
The first step involves ligand-induced receptor dimerization.
Autophosphorylation of receptors gives phosphotyrosine-binding sites for downstream signaling molecules.
Downstream signaling molecules have SH2 domains that bind to specific phosphotyrosine-containing peptides of activated receptors.
SH2 domains were first recognized in tyrosine kinases related to Src, the oncogenic protein of Rous sarcoma virus.
Nonreceptor tyrosine kinases stimulate intracellular tyrosine kinases.
Cytokine receptors share structure with receptor tyrosine kinases, but their cytosolic domains lack catalytic activity.
Ligand binding induces receptor dimerization and cross-phosphorylation of associated nonreceptor tyrosine kinases, which activate the receptor.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Untitled Quiz

Choose a study mode

Podcast

Questions and Answers

How do bacteria and unicellular eukaryotes respond to signals?

In multicellular organisms, cell-cell communication is not very sophisticated.

What initiates a series of reactions that regulate all aspects of cell behavior?

Many cancers arise from problems in signaling pathways.

Much of our understanding of cell signaling comes from the study of healthy cells.

Signaling molecules can range in complexity from ______ to ______.

Which of the following modes of cell signaling involves direct interaction between neighboring cells?

What type of signaling involves molecules released by one cell acting on neighboring target cells?

What is an example of a paracrine signaling molecule?

What type of signaling involves cells responding to signaling molecules that they themselves produce?

Abnormal autocrine signaling is often associated with cancer.

Where can receptors for signaling molecules be located?

What type of molecules do intracellular receptors respond to?

What are some examples of molecules that bind to intracellular receptors?

Steroid hormones are synthesized from cholesterol

Which of the following are considered sex steroids?

What type of steroid hormones are produced by the adrenal gland?

What is an example of a plant steroid hormone?

What is the function of thyroid hormone?

What is the function of Vitamin D3?

What is the function of retinoic acid and retinoids?

What is the nuclear receptor superfamily?

Ligand binding always activates nuclear receptors.

Glucocorticoid receptor is bound to Hsp90 chaperones in the absence of hormone.

What is a common cellular response to the binding of glucocorticoids?

In the absence of hormone, thyroid hormone receptor is associated with a corepressor complex and represses transcription of target genes.

What happens when hormone binds to the thyroid hormone receptor?

Most ligands responsible for cell-cell signaling bind to intracellular receptors.

What is the main function of intracellular signal transduction?

The targets of signaling pathways frequently include transcription factors

What initiates a chain of intracellular reactions in a signaling pathway?

What is the largest family of cell surface receptors?

What is the function of G proteins in cell signalling?

How many subunits do G proteins have?

G proteins are also called heterotrimeric G proteins to distinguish them from other guanine nucleotide-binding proteins.

What are some examples of guanine nucleotide-binding proteins?

How many transmembrane alpha helices do G protein-coupled receptors have?

What type of cellular change occurs when a ligand binds to a G protein-coupled receptor?

What does the activated G protein do?

What is cyclic AMP, and what is its role in cell signalling?

G proteins were discovered during studies of cyclic AMP.

A G protein is an intermediary in adenylyl cyclase activation, which synthesizes cAMP.

What is the role of the alpha subunit in G protein activity?

In its inactive state, the alpha subunit of G proteins is bound to GDP in a complex with beta and gamma subunits.

What causes the exchange of GTP for GDP in G proteins?

After GTP replaces GDP in G proteins, the alpha and beta-gamma complex dissociate from the receptor and interact with their targets.

The activated G protein then phosphorylates its target proteins.

G proteins were discovered during studies of cyclic AMP, which is a second messenger.

What does adenylyl cyclase do?

Cyclic AMP is formed from ATP by adenylyl cyclase and degraded to AMP by cAMP phosphodiesterase.

What is protein kinase A?

Protein kinase A is inactive in the absence of cAMP.

What are the regulatory subunits of protein kinase A?

What happens when the catalytic subunits of protein kinase A are released by the regulatory subunits?

Epinephrine activates the breakdown of glycogen into glucose in muscle cells.

Protein kinases function in isolation

What do protein phosphatases do?

Cyclic AMP can also directly regulate ion channels

What is the role of cyclic AMP in sensing smells?

Other cell surface receptors are directly linked to intracellular enzymes

What are tyrosine kinases?

What are the two types of tyrosine kinases?

The human genome encodes 58 receptor tyrosine kinases.

All receptor tyrosine kinases have an N-terminal extracellular ligand-binding domain, one transmembrane alpha helix, and a cytosolic C-terminal domain with protein-tyrosine kinase activity.

What happens when ligands bind to the extracellular domains of receptor tyrosine kinases?

What is autophosphorylation?

Autophosphorylation of tyrosine in the catalytic domain can increase protein kinase activity.

Autophosphorylation of tyrosine residues outside of the catalytic domain does not create binding sites for other proteins

What are SH2 domains?

Where were SH2 domains first discovered?

Nonreceptor tyrosine kinases do not stimulate intracellular tyrosine kinases.

What does the cytokine receptor superfamily contain?

The structure of cytokine receptors is identical to receptor tyrosine kinases.

What does ligand binding induce in cytokine receptors?

Activated kinases phosphorylate the receptor, providing phosphotyrosine-binding sites for recruitment of downstream signaling molecules with SH2 domains. This helps propagate the signal.

The downstream signaling molecules are not involved in the propagation of the signal.

Signaling molecules can range in complexity from to .