A Cooperative Oxygen Binding Hemoglobin from Mycobacterium tuberculosis: STABILIZATION OF HEME LIGANDS BY A DISTAL TYROSINE RESIDUE

Syun-Ru Yeh,Manon Couture,Yannick Ouellet,Michel Guertin,Denis L Rousseau

doi:10.1074/jbc.275.3.1679

Syun-Ru Yeh, Manon Couture + Show 3 more

Open Access

https://doi.org/10.1074/jbc.275.3.1679

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Abstract

The homodimeric hemoglobin (HbN) from Mycobacterium tuberculosis displays an extremely high oxygen binding affinity and cooperativity. Sequence alignment with other hemoglobins suggests that the proximal F8 ligand is histidine, the distal E7 residue is leucine, and the B10 position is occupied by tyrosine. To determine how these heme pocket residues regulate the ligand binding affinities and physiological functions of HbN, we have measured the resonance Raman spectra of the O(2), CO, and OH(-) derivatives of the wild type protein and the B10 Tyr --> Leu and Phe mutants. Taken together these data demonstrate a unique distal environment in which the heme bound ligands strongly interact with the B10 tyrosine residue. The implications of these data on the physiological functions of HbN and another heme-containing protein, cytochrome c oxidase, are considered.

Highlights

The homodimeric hemoglobin (HbN) from Mycobacterium tuberculosis displays an extremely high oxygen binding affinity and cooperativity
Sequence alignment with other hemoglobins suggests that the proximal F8 ligand is histidine, the distal E7 residue is leucine, and the B10 position is occupied by tyrosine
It is evident from this table that the distal heme pocket of HbN is unique among the globins

Summary

A Cooperative Oxygen Binding Hemoglobin from Mycobacterium tuberculosis

(Received for publication, September 15, 1999, and in revised form, October 20, 1999). Sequence alignment with other hemoglobins suggests that the proximal F8 ligand is histidine, the distal E7 residue is leucine, and the B10 position is occupied by tyrosine To determine how these heme pocket residues regulate the ligand binding affinities and physiological functions of HbN, we have measured the resonance Raman spectra of the O2, CO, and OH؊ derivatives of the wild type protein and the B10 Tyr 3 Leu and Phe mutants. Taken together these data demonstrate a unique distal environment in which the heme bound ligands strongly interact with the B10 tyrosine residue. It displays extremely high oxygen binding affinity and cooperativity, with a Hill coefficient

The abbreviations used are

EXPERIMENTAL PROCEDURES

RESULTS

DISCUSSION