Schiller Martin R, Chakrabarti Kausik, King Glenn F, Schiller Noraisha I, Eipper Betty A, Maciejewski Mark W
Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06019-4301, USA.
J Biol Chem. 2006 Jul 7;281(27):18774-86. doi: 10.1074/jbc.M512482200. Epub 2006 Apr 27.
RhoGEFs are central controllers of small G-proteins in cells and are regulated by several mechanisms. There are at least 22 human RhoGEFs that contain SH3 domains, raising the possibility that, like several other enzymes, SH3 domains control the enzymatic activity of guanine nucleotide exchange factor (GEF) domains through intra- and/or intermolecular interactions. The structure of the N-terminal SH3 domain of Kalirin was solved using NMR spectroscopy, and it folds much like other SH3 domains. However, NMR chemical shift mapping experiments showed that this Kalirin SH3 domain is unique, containing novel cooperative binding site(s) for intramolecular PXXP ligands. Intramolecular Kalirin SH3 domain/ligand interactions, as well as binding of the Kalirin SH3 domain to the adaptor protein Crk, inhibit the GEF activity of Kalirin. This study establishes a novel molecular mechanism whereby intramolecular and intermolecular Kalirin SH3 domain/ligand interactions modulate GEF activity, a regulatory mechanism that is likely used by other RhoGEF family members.
Rho鸟嘌呤核苷酸交换因子（RhoGEFs）是细胞中小G蛋白的核心调控因子，并受多种机制调控。人类至少有22种含SH3结构域的RhoGEFs，这增加了一种可能性，即与其他几种酶一样，SH3结构域通过分子内和/或分子间相互作用控制鸟嘌呤核苷酸交换因子（GEF）结构域的酶活性。使用核磁共振光谱法解析了Kalirin的N端SH3结构域的结构，其折叠方式与其他SH3结构域非常相似。然而，核磁共振化学位移映射实验表明，这种Kalirin SH3结构域是独特的，含有用于分子内PXXP配体的新型协同结合位点。分子内Kalirin SH3结构域/配体相互作用以及Kalirin SH3结构域与衔接蛋白Crk的结合会抑制Kalirin的GEF活性。这项研究建立了一种新的分子机制，即分子内和分子间的Kalirin SH3结构域/配体相互作用调节GEF活性，这是一种其他RhoGEF家族成员可能使用的调控机制。
