1vdh

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spinqualitylabelsall models 1vdh, resolution 2.00Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Structure-based functional identification of a novel heme-binding protein from thermus thermophilus HB8

Overview

The TT1485 gene from Thermus thermophilus HB8 encodes a hypothetical, protein of unknown function with about 20 sequence homologs of bacterial, or archaeal origin. Together they form a family of uncharacterized, proteins, the cluster of orthologous group COG3253. Using a combination of, amino acid sequence analysis, three-dimensional structural studies and, biochemical assays, we identified TT1485 as a novel heme-binding protein., The crystal structure reveals that this protein is a pentamer and each, monomer exhibits a beta-barrel fold. TT1485 is structurally similar to, muconolactone isomerase, but this provided no functional clues. Amino acid, sequence analysis revealed remote homology to a heme enzyme, chlorite, dismutase. Strikingly, amino acid residues that are highly conserved in, the homologous hypothetical proteins and chlorite dismutase cluster around, a deep cavity on the surface of each monomer. Molecular modeling shows, that the cavity can accommodate a heme group with a strictly conserved His, as a heme ligand. TT1485 reconstituted with iron protoporphyrin IX, chloride gave a low chlorite dismutase activity, indicating that TT1485, catalyzes a reaction other than chlorite degradation. The presence of a, possible Fe-His-Asp triad in the heme proximal site suggests that TT1485, functions as a novel heme peroxidase to detoxify hydrogen peroxide within, the cell.

About this Structure

1VDH is a Protein complex structure of sequences from Thermus thermophilus. Full crystallographic information is available from OCA.

Reference

Structure-based functional identification of a novel heme-binding protein from Thermus thermophilus HB8., Ebihara A, Okamoto A, Kousumi Y, Yamamoto H, Masui R, Ueyama N, Yokoyama S, Kuramitsu S, J Struct Funct Genomics. 2005;6(1):21-32. PMID:15965735

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