1vhb

From Proteopedia

Revision as of 15:04, 15 February 2008

BACTERIAL DIMERIC HEMOGLOBIN FROM VITREOSCILLA STERCORARIA

Overview

BACKGROUND: The first hemoglobin identified in bacteria was isolated from, Vitreoscilla stercoraria (VtHb) as a homodimeric species. The wild-type, protein has been reported to display medium oxygen affinity and, cooperative ligand-binding properties. Moreover, VtHb can support aerobic, growth in Escherichia coli with impaired terminal oxidase function. This, ability of VtHb to improve the growth properties of E. coli has important, applications in fermentation technology, assisting the overexpression of, recombinant proteins and antibiotics. Oxygen binding heme domains have, been identified in chimeric proteins from bacteria and yeast, where they, are covalently linked to FAD- and NAD(P)H-binding domains. We investigate, here the fold, the distal heme site structure and the quaternary assembly, of a bacterial hemoglobin which does not bear the typical flavohemoglobin, domain organization. RESULTS: The VtHb three-dimensional structure, conforms to the well known globin fold. Nevertheless, the polypeptide, segment connecting helices C and E is disordered, and residues E7-E10, (defined according to the standard globin fold nomenclature) do not adopt, the usual alpha-helical conformation, thus locating Gln53(E7) out of the, heme pocket. Binding of azide to the heme iron introduces substantial, structural perturbations in the heme distal site residues, particularly, Tyr29(B10) and Pro54(E8). The quaternary assembly of homodimeric VtHb, not, observed before within the globin family, is based on a molecular, interface defined by helices F and H of both subunits, the two heme iron, atoms being 34 A apart. CONCLUSIONS: The unusual heme distal site, structure observed shows that previously undescribed molecular mechanisms, of ligand stabilization are operative in VtHb. The polypeptide chain, disorder observed in the CE region indicates a potential site of, interaction with the FAD/NADH reductase partner, in analogy with, observations in the chimeric flavohemoglobin from Alcaligenes eutrophus.

About this Structure

1VHB is a Single protein structure of sequence from Vitreoscilla stercoraria with as ligand. Full crystallographic information is available from OCA.

Reference

Unusual structure of the oxygen-binding site in the dimeric bacterial hemoglobin from Vitreoscilla sp., Tarricone C, Galizzi A, Coda A, Ascenzi P, Bolognesi M, Structure. 1997 Apr 15;5(4):497-507. PMID:9115439

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