Sopory Shailaja, Balaji S, Srinivasan N, Visweswariah Sandhya S
Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, 560012 Bangalore, India.
FEBS Lett. 2003 Mar 27;539(1-3):161-6. doi: 10.1016/s0014-5793(03)00219-9.
The GAFa domain of the cGMP-binding, cGMP-specific phosphodiesterase (PDE5A) was modeled on the crystal structure of PDE2A GAF domain and residues involved in cGMP binding identified. Tandem GAFa and GAFb domains of PDE5A, expressed in Escherichia coli, bound cGMP (K(d) 27 nM). Mutation of aspartate-299 in GAFa, suggested earlier to be critical for cGMP binding, did not abrogate cGMP binding, but mutation of F205, which formed a stacking interaction with the guanine ring of cGMP, led to complete loss of cGMP binding. Therefore, the GAFa domain of PDE5A adopts a structure similar to the GAFb domain of PDE2A, and provides the sole site for cGMP binding in PDE5A.
以磷酸二酯酶2A（PDE2A）GAF结构域的晶体结构为模板，对环磷酸鸟苷（cGMP）结合特异性磷酸二酯酶（PDE5A）的GAFa结构域进行建模，并确定参与cGMP结合的残基。在大肠杆菌中表达的PDE5A串联GAFa和GAFb结构域与cGMP结合（解离常数K(d)为27 nM）。先前认为对cGMP结合至关重要的GAFa结构域中的天冬氨酸-299突变并未消除cGMP结合，但与cGMP鸟嘌呤环形成堆积相互作用的F205突变导致cGMP结合完全丧失。因此，PDE5A的GAFa结构域采用了与PDE2A的GAFb结构域相似的结构，并为PDE5A中的cGMP结合提供了唯一位点。
