Protein Structure and Function

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Questions and Answers

What is the function of the purple patches in the cell membrane of Halobacterium Halobium?

Fatty acid receptor signaling

Light-driven proton pump involved in photosynthesis (correct)

Regulation of G-protein signaling pathways

Calcitonin receptor activation

What is the protein that occurs naturally as a 2-D crystal in the purple membrane?

Bacteriorhodopsin (correct)

GPCR – β2 adrenergic receptor

GLP-1 Receptor

Calcitonin Receptor

What is the function of β-Arrestin in GPCR signaling pathways?

G-protein deactivation

Receptor activation

Receptor deactivation (correct)

G-protein activation

What is the name of the receptor that is activated by fatty acids?

GPR120 Signup and view all the answers

What is the function of G-proteins in GPCR signaling pathways?

Signal transduction Signup and view all the answers

What is the name of the receptor that is involved in the regulation of blood sugar levels?

GLP-1 Receptor Signup and view all the answers

What is the function of the highly conserved NPA motif in Aquaporin?

To prevent proton conduction Signup and view all the answers

What is the primary feature of the transmembrane structure of the β2 adrenergic receptor?

A covalently attached palmitate linked to an eighth helix Signup and view all the answers

What is the primary difference between G-protein and arrestin pathways in GPCR signaling?

G-protein pathways are rapid and transient, while arrestin pathways are slow and sustained Signup and view all the answers

What is the study that revealed the mechanism of Aquaporin selectivity controlled by Global Orientational Tuning?

Tajkhorshid et al. & Schulten (2002) Signup and view all the answers

What is the primary function of G Protein-Coupled Receptor Kinases (GRK)?

To phosphorylate and desensitize GPCRs Signup and view all the answers

What is the structural feature of the GlpF tetramer viewed from the periplasmic side?

A ribbon representation with a quasi-twofold axis Signup and view all the answers

What is the journal where the study by Fu et al. & Stroud was published?

Science Signup and view all the answers

What is the purpose of the Positive Inside Rule in predicting the topology of transmembrane segments?

To predict the orientation of transmembrane helices Signup and view all the answers

What is the name of the potassium channel studied by Doyle et al. & Mackinnon?

KcsA Signup and view all the answers

What is the primary function of channel proteins and transporters?

To regulate the flow of ions and molecules across the membrane Signup and view all the answers

What is the primary method used to predict transmembrane segments in proteins?

Hydrophobicity plots Signup and view all the answers

What is the purpose of molecular dynamics simulations in the study of Aquaporins?

To understand Aquaporin specificity Signup and view all the answers

Study Notes

GPCR Structure and Function

The β2 adrenergic receptor shows an active vs inactive state, G-protein activation, and β-arrestin activation.
The receptor has a conserved seven-pass transmembrane fold, with a covalently attached palmitate linked to an eighth helix.
The bound ligand carazolol is shown as yellow spheres behind TM6 and TM7.

Class B Family GPCRs

Several structures were reported in 2017, including the Calcitonin Receptor and GLP-1 Receptor.

Fatty Acid Receptor GPCR

The GPR120 receptor was reported in 2023.

Rhodopsin (Bacteriorhodopsin)

Rhodopsin is a 26 kDa protein containing the pigment retinal and functions as a light-driven proton pump in photosynthesis.
The protein occurs naturally as a 2-D crystal about 1 μm in diameter and 45 Å thick.

Integral Membrane Proteins

Hydrophobicity plots can be used to locate TM segments.
TMHMM can predict TM segments.
The positive inside rule can predict the topology of TM segments.

Channel Proteins and Transporters

Channel proteins and transporters are types of integral membrane proteins.

GPCR Signaling

GPCRs can signal through G-protein or arrestin pathways.
GRKs (G-protein-coupled receptor kinases) play a role in GPCR signaling.

Aquaporin

Aquaporin is a channel protein that allows glycerol to pass through the membrane.
The protein has a quasi twofold symmetry, with a channel pathway lined with glycerol molecules.
Molecular dynamics simulations have been used to understand aquaporin specificity.
Aquaporin selectivity is controlled by global orientational tuning.
The NPA motif is highly conserved in aquaporin repeats.
Aquaporin prevents proton conduction.

Potassium Channels

Potassium channels are one of the most common channel types in nature.
The KcsA channel is a simple bacterial potassium channel with a selectivity filter.

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Description

Test your knowledge of protein structure and function, including integral membrane proteins, hydrophobicity plots, and predicting transmembrane segments. Learn about the positive inside rule and non-canonical TM helices.