Donaldson Logan W, Gish Gerald, Pawson Tony, Kay Lewis E, Forman-Kay Julie D
Department of Molecular and Medical Genetics, University of Toronto, Toronto, ON, Canada M5S 1A8.
Proc Natl Acad Sci U S A. 2002 Oct 29;99(22):14053-8. doi: 10.1073/pnas.212518799. Epub 2002 Oct 16.
On phosphorylation of Y221 by Abelson (Abl) kinase, the Crk-II adapter protein undergoes an intramolecular reorganization initiated by the binding of its own Src homology 2 (SH2) domain to the pY221 site. Conformational changes induced by phosphotyrosine recognition promote the binding of the Src homology 3 (SH3) domain of the Abl tyrosine kinase to a proline-rich loop located between the betaD and betaE strands of the SH2 domain (DE loop). We have determined the NMR solution structure of the ternary complex of the Abl SH3 domain with the Crk SH2 domain bound to a Crk pY221 phosphopeptide. The SH2 domain bridges two ligands that bind at distinct sites. The interaction between the Abl SH3 domain and the Crk SH2 domain is localized to a canonical eight-residue site within the DE loop. From (15)N relaxation experiments, the DE loop of the SH2 domain in the complex displays a significant degree of conformational freedom. The structural and dynamic data therefore indicate that these SH2 and SH3 domains do not assume a unique orientation with respect to one another; rather, they appear to be only tethered via the DE loop. Thus, SH2 domain-SH3 domain interactions do not require additional tertiary contacts or restriction of domain orientation when a recognition motif is presented in a mobile loop. This complex between the Abl SH3 domain, Crk SH2 domain, and Crk phosphopeptide is an example of the extremely modular nature of regulatory proteins that provides a rich repertoire of mechanisms for control of biological function.
在阿贝尔森（Abl）激酶使Y221磷酸化后，Crk-II衔接蛋白会发生分子内重排，这一过程由其自身的Src同源2（SH2）结构域与pY221位点结合引发。磷酸酪氨酸识别所诱导的构象变化促进了Abl酪氨酸激酶的Src同源3（SH3）结构域与位于SH2结构域的βD和βE链之间的富含脯氨酸的环（DE环）结合。我们已经确定了Abl SH3结构域与结合了Crk pY221磷酸肽的Crk SH2结构域形成的三元复合物的核磁共振溶液结构。SH2结构域桥接了在不同位点结合的两个配体。Abl SH3结构域与Crk SH2结构域之间的相互作用定位于DE环内一个典型的八残基位点。通过（15）N弛豫实验，复合物中SH2结构域的DE环表现出显著程度的构象自由度。因此，结构和动力学数据表明，这些SH2和SH3结构域彼此之间并没有呈现出独特的取向；相反，它们似乎只是通过DE环相连。因此，当识别基序出现在一个可移动的环中时，SH2结构域-SH3结构域相互作用不需要额外的三级接触或结构域取向的限制。Abl SH3结构域、Crk SH2结构域和Crk磷酸肽之间的这种复合物是调节蛋白极端模块化性质的一个例子，这种性质为生物功能的控制提供了丰富多样的机制。
