This old version of Proteopedia is provided for student assignments while the new version is undergoing repairs. Content and edits done in this old version of Proteopedia after March 1, 2026 will eventually be lost when it is retired in about June of 2026.
Apply for new accounts at the new Proteopedia. Your logins will work in both the old and new versions.
1dj1
From Proteopedia
OCA (Talk | contribs)
(New page: 200px<br /><applet load="1dj1" size="450" color="white" frame="true" align="right" spinBox="true" caption="1dj1, resolution 1.93Å" /> '''CRYSTAL STRUCTURE OF...)
Next diff →
Revision as of 11:11, 20 November 2007
|
CRYSTAL STRUCTURE OF R48A MUTANT OF CYTOCHROME C PEROXIDASE
Overview
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.
About this Structure
1DJ1 is a Single protein structure of sequence from Saccharomyces cerevisiae with HEM as ligand. Active as Cytochrome-c peroxidase, with EC number 1.11.1.5 Full crystallographic information is available from OCA.
Reference
Unusual oxidative chemistry of N(omega)-hydroxyarginine and N-hydroxyguanidine catalyzed at an engineered cavity in a heme peroxidase., Hirst J, Goodin DB, J Biol Chem. 2000 Mar 24;275(12):8582-91. PMID:10722697
Page seeded by OCA on Tue Nov 20 13:19:09 2007
