Publication Abstract from PubMed
In its physiological state, cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) is a tetramer that contains a regulatory (R) subunit dimer and two catalytic (C) subunits. We describe here the 2.3 angstrom structure of full-length tetrameric RIIbeta(2):C(2) holoenzyme. This structure showing a dimer of dimers provides a mechanistic understanding of allosteric activation by cAMP. The heterodimers are anchored together by an interface created by the beta4-beta5 loop in the RIIbeta subunit, which docks onto the carboxyl-terminal tail of the adjacent C subunit, thereby forcing the C subunit into a fully closed conformation in the absence of nucleotide. Diffusion of magnesium adenosine triphosphate (ATP) into these crystals trapped not ATP, but the reaction products, adenosine diphosphate and the phosphorylated RIIbeta subunit. This complex has implications for the dissociation-reassociation cycling of PKA. The quaternary structure of the RIIbeta tetramer differs appreciably from our model of the RIalpha tetramer, confirming the small-angle x-ray scattering prediction that the structures of each PKA tetramer are different.
Structure and allostery of the PKA RIIbeta tetrameric holoenzyme.,Zhang P, Smith-Nguyen EV, Keshwani MM, Deal MS, Kornev AP, Taylor SS Science. 2012 Feb 10;335(6069):712-6. PMID:22323819[1]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
