1DJ5

CRYSTAL STRUCTURE OF R48A MUTANT OF CYTOCHROME C PEROXIDASE WITH N-HYDROXYGUANIDINE BOUND

Summary for 1DJ5

• Entry DOI: 10.2210/pdb1dj5/pdb
• Related: 1DJ1
• Descriptor: CYTOCHROME C PEROXIDASE, PROTOPORPHYRIN IX CONTAINING FE, N-HYDROXYGUANIDINE, ... (4 entities in total)
• Functional Keywords: heme enzyme, cavity mutant, oxidoreductase
• Biological source: Saccharomyces cerevisiae (baker's yeast)
• Cellular location: Mitochondrion matrix: P00431
• Total number of polymer chains: 1
• Total formula weight: 33831.38

Authors

Hirst, J.,Goodin, D.B. (deposition date: 1999-12-01, release date: 1999-12-10, Last modification date: 2024-02-07)

Primary citation

Hirst, J.,Goodin, D.B.
Unusual oxidative chemistry of N(omega)-hydroxyarginine and N-hydroxyguanidine catalyzed at an engineered cavity in a heme peroxidase.
J.Biol.Chem., 275:8582-8591, 2000

PubMed Abstract: Heme enzymes are capable of catalyzing a range of oxidative chemistry with high specificity, depending on the surrounding protein environment. We describe here a reaction catalyzed by a mutant of cytochrome c peroxidase, which is similar but distinct from those catalyzed by nitric-oxide synthase. In the R48A mutant, an expanded water-filled cavity was created above the distal heme face. N-hydroxyguanidine (NHG) but not guanidine was shown to bind in the cavity with K(d) = 8.5 mM, and coordinate to the heme to give a low spin state. Reaction of R48A with peroxide produced a Fe(IV)=O/Trp(.+) center capable of oxidizing either NHG or N(omega)-hydroxyarginine (NHA), but not arginine or guanidine, by a multi-turnover catalytic process. Oxidation of either NHG or NHA by R48A did not result in the accumulation of NO, NO(2)(-), NO(3)(-), urea, or citrulline, but instead afforded a yellow product with absorption maxima of 257 and 400 nm. Mass spectrometry of the derivatized NHA products identified the yellow species as N-nitrosoarginine. We suggest that a nitrosylating agent, possibly derived from HNO, is produced by the oxidation of one molecule of substrate. This then reacts with a second substrate molecule to form the observed N-nitroso products. This complex chemistry illustrates how the active sites of enzymes such as nitric-oxide synthase may serve to prevent alternative reactions from occurring, in addition to enabling those desired.

PubMed: 10722697
DOI: 10.1074/jbc.275.12.8582

Experimental method

X-RAY DIFFRACTION (1.93 Å)