Calmodulin-dependent regulation of inducible and neuronal nitric-oxide synthase

Shiow Ju Lee, James T. Stull

Research output: Contribution to journalArticle

44 Citations (Scopus)

Abstract

Neuronal and endothelial nitric-oxide synthases depend upon Ca2+/calmodulin for activation, whereas the activity of the inducible nitric-oxide synthase is Ca2+-independent, presumably due to tightly bound calmodulin. To study these different mechanisms, a series of chimeras derived from neuronal and inducible nitric-oxide synthases were analyzed. Chimeras containing only the oxygenase domain, calmodulin-binding region, or reductase domain of inducible nitric-oxide synthase did not confer significant Ca2+- independent activity. However, each chimera was more sensitive to Ca2+ than the neuronal isoform. The calmodulin-binding region of inducible nitric- oxide synthase with either its oxygenase or reductase domains resulted in significant, but not total, Ca2+-independent activity. Co- immunoprecipitation experiments showed no calmodulin associated with the former chimera in the absence of Ca2+. Trifluoperazine also inhibited this chimera in the absence of Ca2+. The combined interactions of calmodulin bound to inducible nitric-oxide synthase calmodulin-binding region with the oxygenase domain may be weaker than with the reductase domain. Thus, Ca2+- independent activity of inducible nitric-oxide synthase appears to result from the concerted interactions of calmodulin with both the oxygenase and reductase domains in addition to the canonical calmodulin-binding region. The neuronal isoform is not regulated by a unique autoinhibitory element in its reductase domain.

Original languageEnglish (US)
Pages (from-to)27430-27437
Number of pages8
JournalJournal of Biological Chemistry
Volume273
Issue number42
DOIs
StatePublished - Oct 16 1998

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Nitric Oxide Synthase Type I
Nitric Oxide Synthase Type II
Calmodulin
Oxygenases
Oxidoreductases
Protein Isoforms
Trifluoperazine
Nitric Oxide Synthase Type III
Immunoprecipitation
Chemical activation

ASJC Scopus subject areas

  • Biochemistry

Cite this

Calmodulin-dependent regulation of inducible and neuronal nitric-oxide synthase. / Lee, Shiow Ju; Stull, James T.

In: Journal of Biological Chemistry, Vol. 273, No. 42, 16.10.1998, p. 27430-27437.

Research output: Contribution to journalArticle

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