2j0r

From Proteopedia

Revision as of 16:16, 5 November 2007

STRUCTURE OF THE HAEM-CHAPERONE PROTEOBACTERIA-PROTEIN HEMS

Overview

Bacteria rely on their environment and/or host to acquire iron and have, evolved specialized systems to sequester and transport heme. The heme, uptake system HemRSTUV is common to proteobacteria, and a major challenge, is to understand the molecular mechanism of heme binding and transfer, between the protein molecules that underlie this heme transport relay, process. In the Gram-negative pathogen Yersinia enterocolitica, the, HemRSTUV system culminates with the cytoplasmic recipient HemS, which, stores and delivers heme for cellular needs. HemS belongs to a family of, proteins essential and unique to proteobacteria. Here we report on the, binding mechanism of HemS based on structural data from its apo- and, ligand-loaded forms. This heme carrier protein associates with its cargo, through a novel, partly preformed binding pocket, formed between a large, beta-sheet dome and a three-helix subdomain. In addition to a histidine, interacting with the iron, the complex is stabilized by a distal, non-coordinating arginine that packs along the porphyrin plane and, extensive electrostatic contacts that firmly anchor the heme propionate, groups within the protein. Comparison of apo- and ligand-bound HemS, crystal structures reveals striking conformational changes that underlie a, "heme-induced fit" binding mechanism. Local shifts in amino acid positions, combine with global, rigid body-like domain movements, and together, these, bring about a switch from an open, apo-form to a closed, bound state. This, is the first report in which both liganded and unliganded forms of a heme, transport protein are described, thus providing penetrating insights into, its mechanism of heme binding and release.

About this Structure

2J0R is a Single protein structure of sequence from Yersinia enterocolitica with EDO, PGE, 1PE, 12P and PEG as ligands. Structure known Active Site: AC1. Full crystallographic information is available from OCA.

Reference

An induced fit conformational change underlies the binding mechanism of the heme transport proteobacteria-protein HemS., Schneider S, Sharp KH, Barker PD, Paoli M, J Biol Chem. 2006 Oct 27;281(43):32606-10. Epub 2006 Aug 30. PMID:16943192

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