Podcast
Questions and Answers
What role do autoinhibition mechanisms play in protein kinases?
What role do autoinhibition mechanisms play in protein kinases?
- They increase allosteric interactions.
- They prevent unnecessary activation of the enzyme. (correct)
- They promote substrate binding.
- They enhance phosphorylation efficiency.
Which feature is characteristic of cyclic GMP-dependent protein kinases (cGK) in protozoa?
Which feature is characteristic of cyclic GMP-dependent protein kinases (cGK) in protozoa?
- They may exhibit positive cooperativity. (correct)
- They have multiple phosphorylation sites.
- They are primarily found in mammalian cells.
- They utilize ATP as a primary substrate.
Where is serine 63 located in relation to autophosphorylation in protein kinases?
Where is serine 63 located in relation to autophosphorylation in protein kinases?
- It is adjacent to the myristoylation site.
- It is part of the allosteric binding site.
- It is outside the autophosphorylation sequence. (correct)
- It is within the catalytic domain.
What is a key characteristic of the PKA RIIβ tetrameric holoenzyme structure?
What is a key characteristic of the PKA RIIβ tetrameric holoenzyme structure?
In what context is the term 'myristoylation' relevant to protein kinases?
In what context is the term 'myristoylation' relevant to protein kinases?
Which of the following statements is true regarding phosphoproteomics in malaria research?
Which of the following statements is true regarding phosphoproteomics in malaria research?
What impact does the structure of protein kinases have on their function?
What impact does the structure of protein kinases have on their function?
What is the relationship between cyclic adenosine monophosphate (cAMP) and protein kinase activation?
What is the relationship between cyclic adenosine monophosphate (cAMP) and protein kinase activation?
What structural feature distinguishes PfPKG-b from PfPKG-a in a monomer form?
What structural feature distinguishes PfPKG-b from PfPKG-a in a monomer form?
In the context of AGC kinases, what characteristic is noted about the C terminus in Pf PKG structures?
In the context of AGC kinases, what characteristic is noted about the C terminus in Pf PKG structures?
How does the activation loop of Pf PKG differ from that of PKA?
How does the activation loop of Pf PKG differ from that of PKA?
Which residue in Pf PKG is indicated to become phosphorylated in the presence of cGMP, Mg2+, and ATP?
Which residue in Pf PKG is indicated to become phosphorylated in the presence of cGMP, Mg2+, and ATP?
What role does the proline in the PxxP motif play in Pf PKG as compared to PKA?
What role does the proline in the PxxP motif play in Pf PKG as compared to PKA?
What role does the N-terminal helix, αAK, play in the structure of PKG?
What role does the N-terminal helix, αAK, play in the structure of PKG?
In the structures studied, how does the KD of the Pf PKG compare to other kinase structures?
In the structures studied, how does the KD of the Pf PKG compare to other kinase structures?
What does the overpass in PfPKG-b indicate about the structural differences?
What does the overpass in PfPKG-b indicate about the structural differences?
Which component is involved in the interaction with helix αAK to maintain the inhibition of PKG?
Which component is involved in the interaction with helix αAK to maintain the inhibition of PKG?
What is a significant feature of the kinase domain discovered in all Plasmodium PKG structures?
What is a significant feature of the kinase domain discovered in all Plasmodium PKG structures?
What is a primary structural difference between PKA and PKG?
What is a primary structural difference between PKA and PKG?
Which specific interactions are crucial for maintaining the open conformation of the KD in PKG?
Which specific interactions are crucial for maintaining the open conformation of the KD in PKG?
In what way do CNB-D cGMP-binding domains interact with αAK?
In what way do CNB-D cGMP-binding domains interact with αAK?
What is the significance of the R194C–D241R–D267R triad in relation to PKG?
What is the significance of the R194C–D241R–D267R triad in relation to PKG?
What type of interactions does the C tail participate in concerning PKG's structure?
What type of interactions does the C tail participate in concerning PKG's structure?
Which effect does the structural deviation of αAK have on PKG?
Which effect does the structural deviation of αAK have on PKG?
Flashcards
Cyclic AMP-dependent protein kinase (PKA)
Cyclic AMP-dependent protein kinase (PKA)
An enzyme involved in cellular signaling pathways, activated by cyclic AMP.
PKA structure
PKA structure
The 3D arrangement of atoms in a PKA protein, often relevant to its function.
cGMP-dependent protein kinase (cGK)
cGMP-dependent protein kinase (cGK)
An enzyme activated by cyclic GMP crucial for cellular signaling.
Holoenzyme
Holoenzyme
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Autoinhibition
Autoinhibition
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Autophosphorylation
Autophosphorylation
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Protein Kinases
Protein Kinases
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Crystal Structure determination
Crystal Structure determination
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What is the major structural difference between PKA and PKG?
What is the major structural difference between PKA and PKG?
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What is the role of the N-terminal helix (αAK) in PfPKG-KD?
What is the role of the N-terminal helix (αAK) in PfPKG-KD?
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How does the C-tail interact with the N-terminal helix in PfPKG-KD?
How does the C-tail interact with the N-terminal helix in PfPKG-KD?
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What kind of interactions are involved in PfPKG-KD's autoinhibition?
What kind of interactions are involved in PfPKG-KD's autoinhibition?
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What is the significance of the salt bridges in PfPKG-KD?
What is the significance of the salt bridges in PfPKG-KD?
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What are the similarities between PKA and PKG autoinhibition?
What are the similarities between PKA and PKG autoinhibition?
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How is autoinhibition related to the open or closed conformation of the KD?
How is autoinhibition related to the open or closed conformation of the KD?
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What is the outcome of the interactions between the N-terminal helix, C-tail, and the cGMP-binding domains?
What is the outcome of the interactions between the N-terminal helix, C-tail, and the cGMP-binding domains?
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PfPKG activation loop
PfPKG activation loop
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T695 phosphorylation in PfPKG
T695 phosphorylation in PfPKG
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C-terminus in PfPKG
C-terminus in PfPKG
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PxxP motif in PfPKG
PxxP motif in PfPKG
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Tyrosine motif in PfPKG
Tyrosine motif in PfPKG
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Open conformation of PfPKG activation loop
Open conformation of PfPKG activation loop
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Partial disorder in PfPKG C-terminus
Partial disorder in PfPKG C-terminus
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Study Notes
Malaria Parasite cGMP-Dependent Protein Kinase (PKG) Structure and Activation
- Malaria is a global health concern, with ~500,000 annual deaths.
- The cyclic guanosine-3',5'-monophosphate (cGMP)-dependent protein kinase (PKG) is a potential target for new antimalarial drugs.
- PKG plays a critical role in various stages of the malaria parasite life cycle.
- PfPKG and PvPKG structures determined, revealing a previously unknown activation mechanism.
- The enzyme is predominantly a monomer, not a dimer as previously thought.
Unique Structural Relay Mechanism
- PKG's structure reveals four predicted cyclic nucleotide-binding domains (CNBs) and a kinase domain (KD) arranged in a pentagonal configuration.
- An N-terminal autoinhibitory segment (AIS) is crucial for keeping the kinase inactive.
- CNBs and KD interact to keep the enzyme inactive
- Cooperative binding of cGMP, in a structural relay mechanism, triggers conformational changes around the molecule.
- This enables PKG to orchestrate rapid developmental switches in response to cGMP levels.
Significance of Discovery
- The previously unknown structure of cGMP-free PKG from malaria parasites provides insight into the activation process.
- These structures, coupled to biochemical data, suggest a structural relay activation mechanism involving interdomain communication.
- PKG is a promising drug target for malaria.
cGMP-Free PKG Structures
- Two orthologs (Plasmodium falciparum and Plasmodium vivax) structures (PfPKG and PvPKG) were elucidated, at ~2.4Ã…, in an orthorhombic and monoclinic space group, respectively.
Structure-Activity Relationships and Modeling
- The N-terminal segment exhibits autoinhibitory characteristics. Removal of the segment showed no negative effect on cGMP-mediated activity
- The activation loop is open, an uncommon characteristic for non-phosphorylated AGC kinases
- The c terminus exhibits distinctive features, including a critical proline-rich segment conserved among PfPKG orthologs.
- The study also confirmed that multiple CNBs bind cGMP, with pCNB-C identified as lacking cGMP-binding capability, unlike the other CNBs.
- The crystal structure shows interdomain communication and reveals critical interactions essential for PKG's activation loop.
Molecular Architecture of the Kinase Domain
- The kinase domain (KD) exhibits a characteristic bilobal architecture as observed in PKA and other AGC kinases.
- The activation loop is present in an open conformation, despite lack of phosphorylation, in a manner not previously observed.
- Key structural elements conserved in PKA, like aC-helix, are present, but unique interactions between c-terminal and n-terminal areas of PKG were characterized as contributing to the overall autoinhibited state.
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Description
Explore the structure and activation mechanisms of cGMP-dependent protein kinase (PKG) in malaria parasites. This quiz covers the critical role of PKG in the life cycle of malaria and the discovery of its unique structural relay mechanism. Understand how this knowledge can inform new antimalarial drug development.
