The stimulatory effects of Hofmeister ions on the activities of neuronal nitric-oxide synthase. Apparent substrate inhibition by L-arginine is overcome in the presence of protein-destabilizing agents

Jonathan S. Nishimura, Ramani Narayanasami, R. Timothy Miller, Linda J. Roman, Satya Panda, Bettie Sue S. Masters

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

A variety of monovalent anions and cations were effective in stimulating both calcium ion/calmodulin (Ca2+/CaM)-independent NADPH-cytochrome c reductase activity of, and Ca2+/CaM-dependent nitric oxide (NO·) synthesis by, neuronal nitric oxide synthase (nNOS). The efficacy of the ions in stimulating both activities could be correlated, in general, with their efficacy in precipitating or stabilizing certain proteins, an order referred to as the Hofmeister ion series. In the hemoglobin capture assay, used for measurement of NO· production, apparent substrate inhibition by L-arginine was almost completely reversed by the addition of sodium perchlorate (NaC1O24), one of the more effective protein-destabilizing agents tested. Examination of this phenomenon by the assay of L-arginine conversion to L- citrulline revealed that the stimulatory effect of NaC1O4 on the reaction was observed only in the presence of oxyhemoglobin or superoxide anion (generated by xanthine and xanthine oxidase), both scavengers of NO·. Spectrophotometric examination of nNOS revealed that the addition of NaC1O4 and a superoxide-generating system, but neither alone, prevented the increase of heme absorption at 436 nm, which has been attributed to the nitrosyl complex. The data are consistent with the release of autoinhibitory NO· coordinated to the prosthetic group of nNOS, which, in conjunction with an NO· scavenger, causes stimulation of the reaction.

Original languageEnglish (US)
Pages (from-to)5399-5406
Number of pages8
JournalJournal of Biological Chemistry
Volume274
Issue number9
DOIs
StatePublished - Feb 26 1999

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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