PKA-I holoenzyme structure reveals a mechanism for cAMP-dependent activation
PKA-I holoenzyme structure reveals a mechanism for cAMP-dependent activation
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DOI：
10.1016/j.cell.2007.07.018
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发表时间：
2007-09-21
期刊：
影响因子：
64.5
通讯作者：
Taylor, Susan S.
中科院分区：
文献类型：
--
作者：
Kim, Choel;Cheng, Cecilia Y.;Taylor, Susan S.
蛋白激酶A（PKA）全酶是环磷酸腺苷（cAMP）的主要受体之一，在那里细胞外刺激被翻译成信号应答。我们在这里报告的PKA催化亚基和突变RI调节亚基，RIa（91 - 379：R333 K），含有两个cAMP结合域之间的复合物的结构。在与催化亚基结合后，RI经历了剧烈的构象变化，其中两个cAMP结合结构域解偶联并缠绕在催化亚基的大叶周围。这种大的构象重组揭示了结合和抑制催化亚基所需的协调机制。该结构还揭示了在两个保守残基Glu 261和Arg 366之间的全酶特异性盐桥，其将两个腺嘌呤加帽残基远离其cAMP结合位点。这些残基的突变证明了它们对PKA活化的重要性。我们的结构的见解，结合诱变的结果，提供了一个有序和合作激活PKA的cAMP的分子机制。
Protein kinase A ( PKA) holoenzyme is one of the major receptors for cyclic adenosine monophosphate ( cAMP), where an extracellular stimulus is translated into a signaling response. We report here the structure of a complex between the PKA catalytic subunit and a mutant RI regulatory subunit, RIa( 91 - 379: R333K), containing both cAMP- binding domains. Upon binding to the catalytic subunit, RI undergoes a dramatic conformational change in which the two cAMP- binding domains uncouple and wrap around the large lobe of the catalytic subunit. This large conformational reorganization reveals the concerted mechanism required to bind and inhibit the catalytic subunit. The structure also reveals a holoenzyme- specific salt bridge between two conserved residues, Glu261 and Arg366, that tethers the two adenine capping residues far from their cAMPbinding sites. Mutagenesis of these residues demonstrates their importance for PKA activation. Our structural insights, combined with the mutagenesis results, provide a molecular mechanism for the ordered and cooperative activation of PKA by cAMP.