1ye9
From Proteopedia
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Crystal structure of proteolytically truncated catalase HPII from E. coli
Overview
The large subunit catalase HPII from Escherichia coli can be truncated by, proteolysis to a structure similar to small subunit catalases. Mass, spectrometry analysis indicates that there is some heterogeneity in the, precise cleavage sites, but approximately 74 N-terminal residues, 189, C-terminal residues, and a 9-11-residue internal fragment, including, residues 298-308, are removed. Crystal structure refinement at 2.8 A, reveals that the tertiary and quaternary structure of the native enzyme is, retained with only very subtle changes despite the loss of 36% of the, sequence. The truncated variant exhibits a 1.8 times faster turnover rate, and enhanced sensitivity to high concentrations of H(2)O(2), consistent, with easier access of the substrate to the active site. In addition, the, truncated variant is more sensitive to inhibition, particularly by, reagents such as aminotriazole and azide which are larger than substrate, H(2)O(2). The main channel leading to the heme cavity is largely, unaffected by the truncation, but the lateral channel is shortened and its, entrance widened by removal of the C-terminal domain, providing an, explanation for easier access to the active site. Opening of the entrance, to the lateral channel also opens the putative NADPH binding site, but, NADPH binding could not be demonstrated. Despite the lack of bound NADPH, the compound I species of both native and truncated HPII are reduced back, to the resting state with compound II being evident in the absorbance, spectrum only of the heme b-containing H392A variant.
About this Structure
1YE9 is a Protein complex structure of sequences from Escherichia coli with HDD as ligand. Active as Catalase, with EC number 1.11.1.6 Full crystallographic information is available from OCA.
Reference
Characterization of a large subunit catalase truncated by proteolytic cleavage., Chelikani P, Carpena X, Perez-Luque R, Donald LJ, Duckworth HW, Switala J, Fita I, Loewen PC, Biochemistry. 2005 Apr 19;44(15):5597-605. PMID:15823018
Page seeded by OCA on Wed Nov 21 06:42:53 2007
