1IDR image
Entry Detail
PDB ID:
1IDR
Title:
CRYSTAL STRUCTURE OF THE TRUNCATED-HEMOGLOBIN-N FROM MYCOBACTERIUM TUBERCULOSIS
Biological Source:
Host Organism:
PDB Version:
Deposition Date:
2001-04-05
Release Date:
2001-08-22
Method Details:
Experimental Method:
Resolution:
1.90 Å
R-Value Free:
0.24
R-Value Work:
0.18
R-Value Observed:
0.19
Space Group:
P 21 21 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:HEMOGLOBIN HBN
Chain IDs:A, B
Chain Length:136
Number of Molecules:2
Biological Source:Mycobacterium tuberculosis
Primary Citation
Mycobacterium tuberculosis hemoglobin N displays a protein tunnel suited for O2 diffusion to the heme.
EMBO J. 20 3902 3909 (2001)
PMID: 11483493 DOI: 10.1093/emboj/20.15.3902

Abstact

Macrophage-generated oxygen- and nitrogen-reactive species control the development of Mycobacterium tuberculosis infection in the host. Mycobacterium tuberculosis 'truncated hemoglobin' N (trHbN) has been related to nitric oxide (NO) detoxification, in response to macrophage nitrosative stress, during the bacterium latent infection stage. The three-dimensional structure of oxygenated trHbN, solved at 1.9 A resolution, displays the two-over-two alpha-helical sandwich fold recently characterized in two homologous truncated hemoglobins, featuring an extra N-terminal alpha-helix and homodimeric assembly. In the absence of a polar distal E7 residue, the O2 heme ligand is stabilized by two hydrogen bonds to TyrB10(33). Strikingly, ligand diffusion to the heme in trHbN may occur via an apolar tunnel/cavity system extending for approximately 28 A through the protein matrix, connecting the heme distal cavity to two distinct protein surface sites. This unique structural feature appears to be conserved in several homologous truncated hemoglobins. It is proposed that in trHbN, heme Fe/O2 stereochemistry and the protein matrix tunnel may promote O2/NO chemistry in vivo, as a M.tuberculosis defense mechanism against macrophage nitrosative stress.

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