1h6n

From Proteopedia

Revision as of 14:25, 5 November 2007

FORMATION OF A TYROSYL RADICAL INTERMEDIATE IN PROTEUS MIRABILIS CATALASE BY DIRECTED MUTAGENESIS AND CONSEQUENCES FOR NUCLEOTIDE REACTIVITY

Overview

Heme catalases are homotetrameric enzymes with a highly conserved complex, quaternary structure, and their functional role is still not well, understood. Proteus mirabilis catalase (PMC), a heme enzyme belonging to, the family of NADPH-binding catalases, was efficiently overexpressed in E., coli. The recombinant catalase (rec PMC) was deficient in heme with, one-third heme and two-thirds protoporphyrin IX as determined by mass, spectrometry and chemical methods. This ratio was influenced by the, expression conditions, but the enzyme-specific activity calculated, relative to the heme content remained unchanged. The crystal structure of, rec PMC was solved to a resolution of 2.0 A, the highest resolution, obtained to date with PMC. The overall structure was quite similar to that, of wild-type PMC, and it is surprising that the absence of iron had no, effect on the structure of the active site. Met 53 close to the essential, His 54 was found less oxidized in rec PMC than in the wild-type enzyme. An, acetate anion was modeled in an anionic pocket, away from the heme group, but important for the enzymatic reaction. An alternate conformation, observed for Arg 99 could play a role in the formation of the H-bond, network connecting two symmetrical subunits of the tetramer.

About this Structure

1H6N is a Single protein structure of sequence from Proteus mirabilis with ACT, SO4 and HEM as ligands. Active as Catalase, with EC number 1.11.1.6 Structure known Active Site: HEM. Full crystallographic information is available from OCA.

Reference

High-resolution structure and biochemical properties of a recombinant Proteus mirabilis catalase depleted in iron., Andreoletti P, Sainz G, Jaquinod M, Gagnon J, Jouve HM, Proteins. 2003 Feb 1;50(2):261-71. PMID:12486720

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