TY  - JOUR
N1  - Copyright of this article belongs to ASBMB.
ID  - open1686
UR  - http://www.jbc.org/content/289/31/21573.long
IS  - 31
A1  - Singh, Sandeep
A1  - Thakur, Naveen
A1  - Oliveira, Ana
A1  - Petruk, Ariel A
A1  - Hade, Mangesh Dattu
A1  - Sethi, Deepti
A1  - Bidon-Chanal, Axel
A1  - Martí, Marcelo A
A1  - Datta, Himani
A1  - Parkesh, Raman
A1  - Estrin, Dario A
A1  - Luque, F Javier
A1  - Dikshit, Kanak L
Y1  - 2014/08/01/
N2  - 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 ?M/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.
PB  - ASBMB
JF  - The Journal of biological chemistry
VL  - 289
KW  - Electron Transfer; Hemoglobin; Hemoglobin Myoglobin; Microbial Pathogenesis; Molecular Biology; Mycobacterium Tuberculosis; Nitric Oxide 
SN  - 1083-351X
TI  - 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.
SP  - 21573
EP  - 83
ER  -