TY - JOUR
T1 - A cooperative oxygen-binding hemoglobin from Mycobacterium tuberculosis
AU - Couture, Manon
AU - Yeh, Syun Ru
AU - Wittenberg, Beatrice A.
AU - Wittenberg, Jonathan B.
AU - Ouellet, Yannick
AU - Rousseau, Denis L.
AU - Guertin, Michel
PY - 1999/9/28
Y1 - 1999/9/28
N2 - Two putative hemoglobin genes, glbN and glbO, were recently discovered in the complete genome sequence of Mycobacterium tuberculosis H37Rv. Here, we show that the glbN gene encodes a dimeric hemoglobin (HbN) that binds oxygen cooperatively with very high affinity (P50 = 0.013 mmHg at 20 °C) because of a fast combination (25 μM-1 · s-1) and a slow dissociation (0.2 s- 1) rate. Resonance Raman spectroscopy and ligand association/dissociation kinetic measurements, along with mutagenesis studies, reveal that the stabilization of the bound oxygen is achieved through a tyrosine at the B10 position in the distal pocket of the heme with a conformation that is unique among the globins. Physiological studies performed with Mycobacterium bovis bacillus Calmette-Guerin demonstrate that the expression of HbN is greatly enhanced during the stationary phase in aerobic cultures but not under conditions of limited oxygen availability. The results suggest that, physiologically, the primary role of HbN may be to protect the bacilli against reactive nitrogen species produced by the host macrophage.
AB - Two putative hemoglobin genes, glbN and glbO, were recently discovered in the complete genome sequence of Mycobacterium tuberculosis H37Rv. Here, we show that the glbN gene encodes a dimeric hemoglobin (HbN) that binds oxygen cooperatively with very high affinity (P50 = 0.013 mmHg at 20 °C) because of a fast combination (25 μM-1 · s-1) and a slow dissociation (0.2 s- 1) rate. Resonance Raman spectroscopy and ligand association/dissociation kinetic measurements, along with mutagenesis studies, reveal that the stabilization of the bound oxygen is achieved through a tyrosine at the B10 position in the distal pocket of the heme with a conformation that is unique among the globins. Physiological studies performed with Mycobacterium bovis bacillus Calmette-Guerin demonstrate that the expression of HbN is greatly enhanced during the stationary phase in aerobic cultures but not under conditions of limited oxygen availability. The results suggest that, physiologically, the primary role of HbN may be to protect the bacilli against reactive nitrogen species produced by the host macrophage.
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U2 - 10.1073/pnas.96.20.11223
DO - 10.1073/pnas.96.20.11223
M3 - Article
C2 - 10500158
AN - SCOPUS:0033613114
SN - 0027-8424
VL - 96
SP - 11223
EP - 11228
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 20
ER -