Primary Citation of Related Structures: 1CF9, 1QF7
PubMed Abstract:
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) ...
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.
Related Citations:
Crystal Structure of Catalase HPII from Escherichia Coli Bravo, J., Verdaguer, N., Tormo, J., Betzel, C., Switala, J., Loewen, P.C., Fita, I. (1995) Structure 3: 491
2.8 A Crystal Structure of Catalase Hpii from Escherichia Coli Bravo, J., Tormo, J., Verdaguer, N., Fita, I., Betzel, C., Switala, J., Loewen, P.C. (1993) Acta Crystallogr A 28: 79
Crystallization and Preliminary X-Ray Diffraction Analysis of Catalase Hpii from Escherichia Coli Tormo, J., Fita, I., Switala, J., Loewen, P.C. (1990) J Mol Biol 213: 219
The Refined Structure of Beef Liver Catalase at 2.5 A Resolution Fita, I., Silva, A.M., Murthy, M.R.N., Rossmann, M.G. (1986) Acta Crystallogr B 42: 497
Organizational Affiliation:
CID (Consejo Superior de Investigaciones Cietifícas) Jordi Girona 18-26, 08034 Barcelona, Spain.
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