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Structural basis for endothelial nitric oxide synthase binding to calmodulin
Author(s) -
Aoyagi Mika,
Arvai Andrew S.,
Tainer John A.,
Getzoff Elizabeth D.
Publication year - 2003
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1093/emboj/cdg078
Subject(s) - biology , calmodulin , nitric oxide synthase , nitric oxide synthase type iii , biochemistry , nitric oxide , endothelial nitric oxide synthase , atp synthase , biophysics , microbiology and biotechnology , enzyme , enos , endocrinology
The enzyme nitric oxide synthase (NOS) is exquisitely regulated in vivo by the Ca 2+ sensor protein calmodulin (CaM) to control production of NO, a key signaling molecule and cytotoxin. The differential activation of NOS isozymes by CaM has remained enigmatic, despite extensive research. Here, the crystal lographic structure of Ca 2+ ‐loaded CaM bound to a 20 residue peptide comprising the endothelial NOS (eNOS) CaM‐binding region establishes their individual conformations and intermolecular interactions, and suggests the basis for isozyme‐specific differences. The α‐helical eNOS peptide binds in an antiparallel orientation to CaM through extensive hydrophobic interactions. Unique NOS interactions occur with: (i) the CaM flexible central linker, explaining its importance in NOS activation; and (ii) the CaM C‐terminus, explaining the NOS‐specific requirement for a bulky, hydrophobic residue at position 144. This binding mode expands mechanisms for CaM‐mediated activation, explains eNOS deactivation by Thr495 phosphorylation, and implicates specific hydrophobic residues in the Ca 2+ independence of inducible NOS.