creators_name: Lama, Amrita
creators_name: Pawaria, Sudesh
creators_name: Dikshit, Kanak L
type: article
datestamp: 2012-01-09 04:23:06
lastmod: 2012-01-09 04:23:06
metadata_visibility: show
title: Oxygen binding and NO scavenging properties of truncated hemoglobin, HbN, of Mycobacterium smegmatis.
ispublished: pub
subjects: QR
full_text_status: restricted
keywords: Hemoglobin; HbN; HbO; Nitric oxide; Acidified nitrite; Nitrosative stress; Oxygen uptake; Mycobacterium smegmatis
note: Copyright of this article belongs to Elsevier Science.
abstract: 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.
date: 2006-07-24
date_type: published
publication: FEBS letters
volume: 580
number: 17
publisher: Elsevier Science
pagerange: 4031-41
refereed: TRUE
issn: 0014-5793
official_url: http://www.sciencedirect.com/science/article/pii/S0014579306007447
related_url_url: http://www.sciencedirect.com/science/article/pii/S0014579306007447
related_url_type: pub
citation:   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     
document_url: http://crdd.osdd.net/open/145/1/dikshit2006.pdf