Record Details

Oxygen binding and NO scavenging properties of truncated hemoglobin, HbN, of Mycobacterium smegmatis.

DIR@IMTECH: CSIR-Institute of Microbial Technology

View Archive Info
 
 
Field Value
 
Title Oxygen binding and NO scavenging properties of truncated hemoglobin, HbN, of Mycobacterium smegmatis.
 
Creator Lama, Amrita
Pawaria, Sudesh
Dikshit, Kanak L
 
Subject QR Microbiology
 
Description Unraveling of microbial genome data has indicated that two distantly related truncated hemoglobins (trHbs), HbN and HbO, might occur in many species of slow-growing pathogenic mycobacteria. Involvement of HbN in bacterial defense against NO toxicity and nitrosative stress has been proposed. A gene, encoding a putative HbN homolog with conserved features of typical trHbs, has been identified within the genome sequence of fast-growing mycobacterium, Mycobacterium smegmatis. Sequence analysis of M. smegmatis HbN indicated that it is relatively smaller in size and lacks N-terminal pre-A region, carrying 12-residue polar sequence motif that is present in HbN of M. tuberculosis. HbN encoding gene of M. smegmatis was expressed in E. coli as a 12.8kD homodimeric heme protein that binds oxygen reversibly with high affinity (P50 approximately 0.081 mm Hg) and autooxidizes faster than M. tuberculosis HbN. The circular dichroism spectra indicate that HbN of M. smegmatis and M. tuberculosis are structurally similar. Interestingly, an hmp mutant of E. coli, unable to metabolize nitric oxide, exhibited very low NO uptake activity in the presence of M. smegmatis HbN as compared to HbN of M. tuberculosis. On the basis of cellular heme content, specific nitric oxide dioxygenase (NOD) activity of M. smegmatis HbN was nearly one-third of that from M. tuberculosis. Additionally, the hmp mutant of E. coli, carrying M. smegmatis HbN, exhibited nearly 10-fold lower cell survival under nitrosative stress and nitrite derived reactive nitrogen species as compared to the isogenic strain harboring HbN of M. tuberculosis. Taken together, these results suggest that NO metabolizing activity and protection provided by M. smegmatis HbN against toxicity of NO and reactive nitrogen is significantly lower than HbN of M. tuberculosis. The lower efficiency of M. smegmatis HbN for NO detoxification as compared to M. tuberculosis HbN might be related to different level of NO exposure and nitrosative stress faced by these mycobacteria during their cellular metabolism.
 
Publisher Elsevier Science
 
Date 2006-07-24
 
Type Article
PeerReviewed
 
Format application/pdf
 
Identifier http://crdd.osdd.net/open/145/1/dikshit2006.pdf
Lama, Amrita and Pawaria, Sudesh and Dikshit, Kanak L (2006) Oxygen binding and NO scavenging properties of truncated hemoglobin, HbN, of Mycobacterium smegmatis. FEBS letters, 580 (17). pp. 4031-41. ISSN 0014-5793
 
Relation http://www.sciencedirect.com/science/article/pii/S0014579306007447
http://crdd.osdd.net/open/145/