Singh, Sandeep and Thakur, Naveen and Oliveira, Ana and Petruk, Ariel A and Hade, Mangesh Dattu and Sethi, Deepti and Bidon-Chanal, Axel and Martí, Marcelo A and Datta, Himani and Parkesh, Raman and Estrin, Dario A and Luque, F Javier and Dikshit, Kanak L (2014) Mechanistic insight into the enzymatic reduction of truncated hemoglobin N of Mycobacterium tuberculosis: role of the CD loop and pre-A motif in electron cycling. The Journal of biological chemistry, 289 (31). pp. 21573-83. ISSN 1083-351X
Full text not available from this repository. (Request a copy)Abstract
Many pathogenic microorganisms have evolved hemoglobin-mediated nitric oxide (NO) detoxification mechanisms, where a globin domain in conjunction with a partner reductase catalyzes the conversion of toxic NO to innocuous nitrate. The truncated hemoglobin HbN of Mycobacterium tuberculosis displays a potent NO dioxygenase activity despite lacking a reductase domain. The mechanism by which HbN recycles itself during NO dioxygenation and the reductase that participates in this process are currently unknown. This study demonstrates that the NADH-ferredoxin/flavodoxin system is a fairly efficient partner for electron transfer to HbN with an observed reduction rate of 6.2 μM/min(-1), which is nearly 3- and 5-fold faster than reported for Vitreoscilla hemoglobin and myoglobin, respectively. Structural docking of the HbN with Escherichia coli NADH-flavodoxin reductase (FdR) together with site-directed mutagenesis revealed that the CD loop of the HbN forms contacts with the reductase, and that Gly(48) may have a vital role. The donor to acceptor electron coupling parameters calculated using the semiempirical pathway method amounts to an average of about 6.4 10(-5) eV, which is lower than the value obtained for E. coli flavoHb (8.0 10(-4) eV), but still supports the feasibility of an efficient electron transfer. The deletion of Pre-A abrogated the heme iron reduction by FdR in the HbN, thus signifying its involvement during intermolecular interactions of the HbN and FdR. The present study, thus, unravels a novel role of the CD loop and Pre-A motif in assisting the interactions of the HbN with the reductase and the electron cycling, which may be vital for its NO-scavenging function.
| Item Type: | Article |
|---|---|
| Additional Information: | Copyright of this article belongs to ASBMB. |
| Uncontrolled Keywords: | Electron Transfer; Hemoglobin; Hemoglobin Myoglobin; Microbial Pathogenesis; Molecular Biology; Mycobacterium Tuberculosis; Nitric Oxide |
| Subjects: | Q Science > QR Microbiology |
| Depositing User: | Dr. K.P.S.Sengar |
| Date Deposited: | 20 Jul 2015 04:51 |
| Last Modified: | 20 Jul 2015 04:51 |
| URI: | http://crdd.osdd.net/open/id/eprint/1686 |
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