Structural basis for endothelial nitric oxide synthase binding to calmodulin

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 c...

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Bibliographic Details
Published in:The EMBO journal 2003-02, Vol.22 (4), p.766-775
Main Authors: Aoyagi, Mika, Arvai, Andrew S., Tainer, John A., Getzoff, Elizabeth D.
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Binding Sites - genetics
calcium
Calcium - metabolism
calmodulin
Calmodulin - chemistry
Calmodulin - metabolism
crystal structure
Crystallography, X-Ray
EMBO37
EMBO40
Endothelium - chemistry
Endothelium - metabolism
Enzyme Activation - physiology
intermolecular interaction
Isoenzymes - metabolism
Molecular Sequence Data
nitric oxide synthase
Nitric Oxide Synthase - chemistry
Nitric Oxide Synthase - genetics
Nitric Oxide Synthase - metabolism
Nitric Oxide Synthase Type III
Phosphorylation
Protein Binding
Protein Conformation
Rats
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Summary: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.
ISSN:0261-4189
1460-2075
1460-2075
DOI:10.1093/emboj/cdg078