3P9P: Structure of I274V variant of E. coli KatE

Citation:
Abstract
Heme-containing catalases have been extensively studied, revealing the roles of many residues, the existence of two heme orientations, flipped 180 degrees relative to one another along the propionate-vinyl axis, and the presence of both heme b and heme d. The focus of this report is a residue, situated adjacent to the vinyl groups of the heme at the entrance of the lateral channel, with an unusual main chain geometry that is conserved in all catalase structures so far determined. In Escherichia coli catalase HPII, the residue is Ile274, and replacing it with Gly, Ala, and Val, found at the same location in other catalases, results in a reduction in catalytic efficiency, a reduced intensity of the Soret absorbance band, and a mixture of heme orientations and species. The reduced turnover rates and higher H(2)O(2) concentrations required to attain equivalent reaction velocities are explained in terms of less efficient containment of substrate H(2)O(2) in the heme cavity arising from easier escape through the more open entrance to the lateral channel created by the smaller side chains of Gly and Ala. Inserting a Cys at position 274 resulted in the heme being covalently linked to the protein through a Cys-vinyl bond that is hypersensitive to X-ray irradiation being largely degraded within seconds of exposure to the X-ray beam. Two heme orientations, flipped along the propionate-vinyl axis, are found in the Ala, Val, and Cys variants.
PDB ID: 3P9PDownload
MMDB ID: 87505
PDB Deposition Date: 2010/10/18
Updated in MMDB: 2010/12
Experimental Method:
x-ray diffraction
Resolution: 1.5  Å
Source Organism:
Similar Structures:
Biological Unit for 3P9P: tetrameric; determined by author and by software (PISA)
Molecular Components in 3P9P
Label Count Molecule
Proteins (4 molecules)
4
Catalase Hpii(Gene symbol: katE)
Molecule annotation
Chemicals (16 molecules)
1
8
2
4
3
4
* Click molecule labels to explore molecular sequence information.

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