title: Structural determinants of ligand migration in Mycobacterium tuberculosis truncated hemoglobin O.
abstract: Mycobacterium tuberculosis is the causative agent of human tuberculosis, one of the most prevalent infectious diseases in the world. Its genome hosts the glbN and glbO genes coding for two proteins, truncated hemoglobin N (trHbN) and truncated hemoglobin O (trHbO), that belong to different groups (I and II, respectively) of the recently discovered trHb family of hemeproteins. The different expression pattern and kinetics rates constants for ligand association and NO oxidation rate suggest different functions for these proteins. Previous experimental and theoretical studies showed that, in trHbs, ligand migration along the internal tunnel cavity system is a key issue in determining the ligand-binding characteristics. The X-ray structure of trHbO has been solved and shows several internal cavities and secondary-docking sites. In this work, we present an extensive investigation of the tunnel/cavity system ofM. tuberculosis trHbO by means of computer-simulation techniques. We have computed the free-energy profiles for ligand migration along three found tunnels in the oxy and deoxy w.t. and mutant trHbO proteins. Our results show that multiple-ligand migration paths are possible and that several conserved residues such as TrpG8 play a key role in the ligand-migration regulation.
authors.affiliation: Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Pabellón II, Buenos Aires, Argentina.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Boechi
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Martí
authors.forename: Mario
authors.initials: M
authors.lastname: Milani
authors.forename: Martino
authors.initials: M
authors.lastname: Bolognesi
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Luque
authors.forename: Darío A
authors.initials: DA
authors.lastname: Estrin
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D018360:Crystallography, X-Ray; D008024:Ligands; D050505:Mutant Proteins / Q000737:chemistry* / Q000235:genetics; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism*; D013816:Thermodynamics; D054793:Truncated Hemoglobins / Q000737:chemistry* / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C102539:GlbN protein, bacteria; D008024:Ligands; D050505:Mutant Proteins; D054793:Truncated Hemoglobins