Lobe-specific calcium binding in calmodulin regulates endothelial nitric oxide synthase activation.

ABSTRACT:

Background

Human endothelial nitric oxide synthase (eNOS) requires calcium-bound calmodulin (CaM) for electron transfer but the detailed mechanism remains unclear.

Methodology/principal findings

Using a series of CaM mutants with E to Q substitution at the four calcium-binding sites, we found that single mutation at any calcium-binding site (B1Q, B2Q, B3Q and B4Q) resulted in ∼2-3 fold increase in the CaM concentration necessary for half-maximal activation (EC50) of citrulline formation, indicating that each calcium-binding site of CaM contributed to the association between CaM and eNOS. Citrulline formation and cytochrome c reduction assays revealed that in comparison with nNOS or iNOS, eNOS was less stringent in the requirement of calcium binding to each of four calcium-bi

SUBMITTER: Wu PR 

PROVIDER: S-EPMC3387242 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature