Nitric oxide: a radical molecule in quest of free radicals in proteins

Citation
O. Guittet et al., Nitric oxide: a radical molecule in quest of free radicals in proteins, CELL MOL L, 55(8-9), 1999, pp. 1054-1067
Citations number
75
Categorie Soggetti
Cell & Developmental Biology
Journal title
CELLULAR AND MOLECULAR LIFE SCIENCES
ISSN journal
1420682X → ACNP
Volume
55
Issue
8-9
Year of publication
1999
Pages
1054 - 1067
Database
ISI
SICI code
1420-682X(199907)55:8-9<1054:NOARMI>2.0.ZU;2-S
Abstract
A number of enzymes use an amino acid free radical cofactor. Tyrosyl and tr yptophanyl radicals react with nitric oxide (NO) with an almost diffusion-l imited rate. The catalytically competent tyrosyl radical in ribonucleotide reductase (RR) and prostaglandin H synthase (PGHS) recombines with NO in a radical-radical reaction. The unstable adduct formed can dissociate to rege nerate the tyrosyl radical. However, upon prolonged incubation with NO, the diiron center of mouse RR leaks out, while the adduct is sucessively oxidi zed into an iminoxyl radical and a nitrotyrosine in PGHS. These data provid e a plausible mechanism for the physiological inactivation of RR observed i n various models, and may help in understanding the inhibition of PGHS repo rted in some cases. Reversible combination with NO is an intrinsic property of tyrosyl radicals, which also occurs with Y-D(.) and Y-Z(.) in photosyst em II, where NO has been useful in the analysis of the oxygen-evolving comp lex.