2fxh

From Proteopedia

proteopedia linkproteopedia link

spinqualitylabelsall models 2fxh, resolution 1.90Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Crystal structure of KatG at pH 6.5

Overview

Crystals of Burkholderia pseudomallei KatG retain their ability to, diffract X-rays at high resolution after adjustment of the pH from 5.6 to, 4.5, 6.5, 7.5, and 8.5, providing a unique view of the effect of pH on, protein structure. One significant pH-sensitive change lies in the, appearance of a perhydroxy group attached to the indole nitrogen of the, active site Trp111 above pH 7, similar to a modification originally, observed in the Ser324Thr variant of the enzyme at pH 5.6. The, modification forms rapidly from molecular oxygen in the buffer with 100%, occupancy after one minute of soaking of the crystal at room temperature, and pH 8.5. The low temperature (4 K) ferric EPR spectra of the resting, enzyme, being very sensitive to changes in the heme iron microenvironment, confirm the presence of the modification above pH 7 in native enzyme and, variants lacking Arg426 or Met264 and its absence in variants lacking, Trp111 or Tyr238. The indole-perhydroxy group is very likely the reactive, intermediate of molecular oxygen in the NADH oxidase reaction, and Arg426, is required for its reduction. The second significant pH-sensitive change, involves the buried side chain of Arg426 that changes from one predominant, conformation at low pH to a second at high pH. The pH profiles of the, peroxidase, catalase, and NADH oxidase reactions can be correlated with, the distribution of Arg426 conformations. Other pH-induced structural, changes include a number of surface-situated side chains, but there is, only one change involving a displacement of main chain atoms triggered by, the protonation of His53 in a deep pocket in the vicinity of the molecular, 2-fold axis.

About this Structure

2FXH is a Single protein structure of sequence from Burkholderia pseudomallei with , , and as ligands. Active as Catalase, with EC number 1.11.1.6 Full crystallographic information is available from OCA.

Reference

Roles for Arg426 and Trp111 in the modulation of NADH oxidase activity of the catalase-peroxidase KatG from Burkholderia pseudomallei inferred from pH-induced structural changes., Carpena X, Wiseman B, Deemagarn T, Herguedas B, Ivancich A, Singh R, Loewen PC, Fita I, Biochemistry. 2006 Apr 25;45(16):5171-9. PMID:16618106

Page seeded by OCA on Tue Jan 29 19:46:56 2008