#protein kinase A

Membrane Transportation

The regulatory (R) domain of CFTR is phosphorylated by:

Regulatory R domain of CFTR spanning approximately residues 590 to 850 is an intrinsically disordered segment bridging NBD1 and TMD2 containing numerous consensus PKA and PKC phosphorylation sites. Phosphorylation is central to activation. Elevated intracellular cAMP activates protein kinase A which phosphorylates serines including Ser660, Ser737, Ser795, Ser813 and Ser768, neutralizing inhibitory interactions between R domain and NBDs and between NBD1-NBD2 interface. This conformational unblocking permits ATP binding to NBDs, dimer formation, and pore opening. Protein kinase C, Ca2+/calmoduli

Ref: Hwang & Sheppard, Trends Pharmacol Sci 2009, CFTR R domain regulation; Riordan, Annu Rev Biochem 2008.

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A Cell Signaling

Which statement about PKA is NOT correct?

cAMP binding strengthens R–C interaction, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Signaling GPCR Pathways - I

Inactive PKA holoenzyme consists of

Inactive protein kinase A is a tetramer of two regulatory and two catalytic subunits. Binding of four molecules of cAMP to the regulatory subunits induces a conformational change that releases the catalytic subunits. Free catalytic subunits then phosphorylate downstream substrates. Reassociation of the holoenzyme occurs when cAMP levels fall, restoring the inactive state.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Signaling GPCR Pathways - I

PKA is activated by binding of

cAMP, is consistent with established principles of cell signaling, receptor pharmacology and cellular regulation. Experimental measurements of binding parameters, genetic loss-of-function studies and pharmacological interventions all converge on the same interpretation. Related options address neighboring concepts but do not satisfy the precise criterion stated in the question.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Signaling GPCR Pathways - I

PKA activation involves

Inactive protein kinase A is a tetramer of two regulatory and two catalytic subunits. Binding of four molecules of cAMP to the regulatory subunits induces a conformational change that releases the catalytic subunits. Free catalytic subunits then phosphorylate downstream substrates. Reassociation of the holoenzyme occurs when cAMP levels fall, restoring the inactive state.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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Cell Signaling GPCR Pathways - I

cAMP directly activates

Cyclic AMP binds the regulatory subunits of protein kinase A, releasing the catalytic subunits that then phosphorylate serine and threonine residues on target proteins. This activation mechanism couples Gs-mediated stimulation of adenylyl cyclase to the phosphorylation of enzymes, ion channels and transcription factors, thereby translating the extracellular signal into diverse cellular responses.

Ref: NCERT Biology Class 11–12 Alberts et al Molecular Biology of the Cell Lodish et al, Molecular Cell Biology Cooper & Hausman, The Cell Abbas et al., Cellular and Molecular Immunology (for immunology sections)

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