title: Using Markov state models to develop a mechanistic understanding of protein kinase A regulatory subunit RIα activation in response to cAMP binding.
abstract: Protein kinase A (PKA) holoenzyme consists of two catalytic (C) subunits and a regulatory (R) subunit dimer (R(2)C(2)). The kinase is activated by the binding of cAMPs to the two cyclic nucleotide binding domains (CBDs), A and B, on each R-subunit. Despite extensive study, details of the allosteric mechanisms underlying the cooperativity of holoenzyme activation remain unclear. Several Markov state models of PKA-RIα were developed to test competing theories of activation for the R(2)C(2) complex. We found that CBD-B plays an essential role in R-C interaction and promotes the release of the first C-subunit prior to the binding to CBD-A. This favors a conformational selection mechanism for release of the first C-subunit of PKA. However, the release of the second C-subunit requires all four cAMP sites to be occupied. These analyses elucidate R-C heterodimer interactions in the cooperative activation of PKA and cAMP binding and represent a new mechanistic model of R(2)C(2) PKA-RIα activation.
authors.affiliation: From the Departments of Bioengineering.
authors.forename: Britton W
authors.initials: BW
authors.lastname: Boras
authors.affiliation: Chemistry and Biochemistry.
authors.forename: Alexandr
authors.initials: A
authors.lastname: Kornev
authors.affiliation: Chemistry and Biochemistry, Pharmacology, and.
authors.forename: Susan S
authors.initials: SS
authors.lastname: Taylor
authors.affiliation: From the Departments of Bioengineering, Medicine, University of California, San Diego, La Jolla, California 92093 amcculloch@ucsd.edu.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: McCulloch
mesh_terms: D000242:Cyclic AMP / Q000378:metabolism*; D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D008390:Markov Chains; D008958:Models, Molecular; D050505:Mutant Proteins / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D055503:Protein Multimerization / Q000187:drug effects; D017434:Protein Structure, Tertiary; D015203:Reproducibility of Results
chemical_list: D054756:Cyclic AMP-Dependent Protein Kinase RIalpha Subunit; D050505:Mutant Proteins; D009842:Oligopeptides; C037642:kemptide; D000242:Cyclic AMP
keywords: Allosteric Regulation; Computer Modeling; Cooperativity; Cyclic AMP (cAMP); Protein Kinase A (PKA)