title: A cooperative oxygen binding hemoglobin from Mycobacterium tuberculosis. Stabilization of heme ligands by a distal tyrosine residue.
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.
authors.affiliation: Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA. syeh@aecom.yu.edu
authors.forename: S R
authors.initials: SR
authors.lastname: Yeh
authors.forename: M
authors.initials: M
authors.lastname: Couture
authors.forename: Y
authors.initials: Y
authors.lastname: Ouellet
authors.forename: M
authors.initials: M
authors.lastname: Guertin
authors.forename: D L
authors.initials: DL
authors.lastname: Rousseau
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry; D006418:Heme / Q000737:chemistry*; D006454:Hemoglobins / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D006878:Hydroxides / Q000737:chemistry; D008024:Ligands; D008956:Models, Chemical; D009169:Mycobacterium tuberculosis / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry; D013059:Spectrum Analysis, Raman; D014443:Tyrosine / Q000737:chemistry
chemical_list: D006454:Hemoglobins; D006878:Hydroxides; D008024:Ligands; D011994:Recombinant Proteins; D014443:Tyrosine; D006418:Heme; D002248:Carbon Monoxide; D006859:Hydrogen; C031356:hydroxide ion; D010100:Oxygen