1cf9
From Proteopedia
STRUCTURE OF THE MUTANT VAL169CYS OF CATALASE HPII FROM ESCHERICHIA COLI
Overview
The three-dimensional structures of two HPII variants, V169C and H392Q, have been determined at resolutions of 1.8 and 2.1 A, respectively. The V169C variant contains a new type of covalent bond between the sulfur atom of Cys(169) and a carbon atom on the imidazole ring of the essential His(128). This variant enzyme has only residual catalytic activity and contains heme b. The chain of water molecules visible in the main channel may reflect the organization of the hydrogen peroxide substrates in the active enzyme. Two alternative mechanisms, involving either compound I or free radical intermediates, are presented to explain the formation of the Cys-His covalent bond. The H392Q and H392E variants exhibit 75 and 25% of native catalytic activity, respectively. The Gln(392) variant contains only heme b, whereas the Glu(392) variant contains a mixture of heme b and cis and trans isomers of heme d, suggesting of a role for this residue in heme conversion. Replacement of either Gln(419) and Ser(414), both of which interact with the heme, affected the cis:trans ratio of spirolactone heme d. Implications for the heme oxidation mechanism and the His-Tyr bond formation in HPII are considered.
About this Structure
1CF9 is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Mutants that alter the covalent structure of catalase hydroperoxidase II from Escherichia coli., Mate MJ, Sevinc MS, Hu B, Bujons J, Bravo J, Switala J, Ens W, Loewen PC, Fita I, J Biol Chem. 1999 Sep 24;274(39):27717-25. PMID:10488114 Page seeded by OCA on Fri May 2 12:40:12 2008
