蛋白激酶A的RIα亚基：无环磷酸腺苷（cAMP）结构揭示了将cAMP对接至位点B的疏水封端机制。

RIalpha subunit of PKA: a cAMP-free structure reveals a hydrophobic capping mechanism for docking cAMP into site B.

作者信息

Wu Jian, Brown Simon, Xuong Nguyen-Huu, Taylor Susan S

机构信息

Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA 92093, USA.

出版信息

Structure. 2004 Jun;12(6):1057-65. doi: 10.1016/j.str.2004.03.022.

DOI:10.1016/j.str.2004.03.022

PMID:15274925

Abstract

In eukaryotes the primary target for cAMP, a ubiquitous second messenger, is cAMP-dependent protein kinase (PKA). Understanding how binding and release of cAMP changes the cAMP binding domains and then triggers long-range allosteric responses is an important challenge. This conformational switching requires structure solutions of cAMP binding domains in cAMP-bound and cAMP-free states. We describe for the first time a crystal structure of the cAMP binding domains of PKA type Ialpha regulatory subunit where site A is occupied by cGMP and site B is unoccupied. The structure reveals that the carboxyl terminus of domain B serves as a hydrophobic cap, locking the cyclic nucleotide via its adenine ring into the beta-barrel. In the absence of cAMP, the "cap" is released via an extension of the C-terminal helix. This simple hinge mechanism for binding and release of cAMP also provides a mechanism for allosteric communication between sites A and B.

摘要

在真核生物中，环磷酸腺苷（cAMP，一种普遍存在的第二信使）的主要作用靶点是环磷酸腺苷依赖性蛋白激酶（PKA）。了解cAMP的结合与释放如何改变其结合结构域，进而引发长程别构反应，是一项重大挑战。这种构象转换需要获得cAMP结合结构域在结合cAMP和未结合cAMP状态下的结构解析。我们首次描述了Iα型PKA调节亚基的cAMP结合结构域的晶体结构，其中A位点被环磷酸鸟苷（cGMP）占据，B位点未被占据。该结构表明，结构域B的羧基末端充当疏水帽，通过其腺嘌呤环将环核苷酸锁定在β桶中。在没有cAMP的情况下，“帽”通过C末端螺旋的延伸而释放。这种简单的cAMP结合与释放的铰链机制也为A位点和B位点之间的别构通讯提供了一种机制。