Wu Jian, Brown Simon H J, von Daake Sventja, Taylor Susan S
Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.
Science. 2007 Oct 12;318(5848):274-9. doi: 10.1126/science.1146447.
The catalytic (C) subunit of cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) is inhibited by two classes of regulatory subunits, RI and RII. The RII subunits are substrates as well as inhibitors and do not require adenosine triphosphate (ATP) to form holoenzyme, which distinguishes them from RI subunits. To understand the molecular basis for isoform diversity, we solved the crystal structure of an RIIalpha holoenzyme and compared it to the RIalpha holoenzyme. Unphosphorylated RIIalpha(90-400), a deletion mutant, undergoes major conformational changes as both of the cAMP-binding domains wrap around the C subunit's large lobe. The hallmark of this conformational reorganization is the helix switch in domain A. The C subunit is in an open conformation, and its carboxyl-terminal tail is disordered. This structure demonstrates the conserved and isoform-specific features of RI and RII and the importance of ATP, and also provides a new paradigm for designing isoform-specific activators or antagonists for PKA.
环磷酸腺苷（cAMP）依赖性蛋白激酶（PKA）的催化（C）亚基受到两类调节亚基RI和RII的抑制。RII亚基既是底物又是抑制剂，形成全酶时不需要三磷酸腺苷（ATP），这使其有别于RI亚基。为了解亚型多样性的分子基础，我们解析了RIIα全酶的晶体结构，并将其与RIα全酶进行比较。未磷酸化的RIIα（90 - 400）缺失突变体发生了主要的构象变化，因为两个cAMP结合结构域都环绕在C亚基的大结构域周围。这种构象重组的标志是结构域A中的螺旋转换。C亚基处于开放构象，其羧基末端尾巴无序。该结构展示了RI和RII的保守及亚型特异性特征以及ATP的重要性，还为设计PKA亚型特异性激活剂或拮抗剂提供了新的范例。
