PDBsum entry 1vhb

Oxygen transport

PDB id: 1vhb

Contents

Protein chains

135 a.a. *

Ligands

HEM ×2

Waters ×119

* Residue conservation analysis

PDB id:

1vhb

Name:

Oxygen transport

Title:

Bacterial dimeric hemoglobin from vitreoscilla stercoraria

Structure:

Hemoglobin. Chain: a, b. Synonym: soluble cytochrome o. Engineered: yes

Source:

Vitreoscilla stercoraria. Organism_taxid: 61. Strain: c1. Atcc: 15218. Gene: vgb. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.83Å R-factor: 0.184 R-free: 0.250

Authors:

C.Tarricone,A.Galizzi,A.Coda,P.Ascenzi,M.Bolognesi

Key ref:

C.Tarricone et al. (1997). Unusual structure of the oxygen-binding site in the dimeric bacterial hemoglobin from Vitreoscilla sp. Structure, 5, 497-507. PubMed id: 9115439 DOI: 10.1016/S0969-2126(97)00206-2

Date:

19-Feb-97 Release date: 25-Feb-98

Protein chains

P04252  (BAHG_VITST) -  Bacterial hemoglobin from Vitreoscilla stercoraria

Seq: 146 a.a.

Struc: 135 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1016/S0969-2126(97)00206-2

Structure 5:497-507 (1997)

PubMed id: 9115439

Unusual structure of the oxygen-binding site in the dimeric bacterial hemoglobin from Vitreoscilla sp.

C.Tarricone, A.Galizzi, A.Coda, P.Ascenzi, M.Bolognesi.

ABSTRACT

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.

Selected figure(s)

Figure 5.
Figure 5. A structural overlay of one VtHb subunit (red) onto the 1-272 region of Alcaligenes flavoHb, comprising the heme domain (green) and the FAD-binding region in the C-terminal domain (dark green). For clarity, only the heme group of VtHb is shown, and the NADP-binding region of flavoHb (residues 273-403) is not shown. The adenine portion of FAD (yellow) in the upper part of the picture, points towards the CE regions of flavoHb (yellow) and towards the 9-residue disordered CE segment of VtHb. (The figure was drawn using the program MOLSCRIPT [68].)

The above figure is reprinted by permission from Cell Press: Structure (1997, 5, 497-507) copyright 1997.

Figure was selected by an automated process.