Role of pre-A motif in nitric oxide scavenging by truncated hemoglobin, HbN, of Mycobacterium tuberculosis

Mycobacterium tuberculosis truncated hemoglobin, HbN, is endowed with a potent nitric-oxide dioxygenase activity and has been found to relieve nitrosative stress and enhance in vivo survival of a heterologous host, Salmonella enterica Typhimurium, within the macrophages. These findings implicate inv...

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Detalles Bibliográficos
Autores principales: Lama, A., Pawaria, S., Bidon-Chanal, A., Anand, A., Gelpi, J.L., Arya, S., Marti, M., Estrin, D.A., Luque, F.J., Dikshit, K.L.
Formato: JOUR
Materias:
Active site
Dioxygenase
In-vivo
M. tuberculosis
Molecular dynamics simulations
Mycobacterium smegmatis
Mycobacterium tuberculosis
Nitrosative stress
Protein dynamics
Salmonella enterica
Truncated hemoglobins
Detoxification
Dynamics
Ligands
Molecular dynamics
Nitric oxide
Porphyrins
Hemoglobin
dioxygenase
heme
hemoglobin HbN
nitric oxide
truncated hemoglobin
unclassified drug
mutant protein
scavenger
amino terminal sequence
article
controlled study
detoxification
enzyme active site
enzyme activity
ligand binding
molecular dynamics
nitric oxide scavenging
nitrosative stress
nonhuman
Pre A motif
priority journal
protein analysis
protein folding
protein function
protein interaction
protein metabolism
protein motif
protein structure
protein transport
stoichiometry
amino acid sequence
chemical structure
chemistry
circular dichroism
computer simulation
drug effect
Escherichia coli
gene deletion
metabolism
molecular genetics
oxidation reduction reaction
pliability
protein secondary structure
structure activity relation
thermodynamics
X ray crystallography
Amino Acid Motifs
Amino Acid Sequence
Circular Dichroism
Computer Simulation
Crystallography, X-Ray
Free Radical Scavengers
Models, Molecular
Molecular Sequence Data
Mutant Proteins
Nitric Oxide
Oxidation-Reduction
Pliability
Protein Structure, Secondary
Sequence Deletion
Structure-Activity Relationship
Thermodynamics
Truncated Hemoglobins
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00219258_v284_n21_p14457_Lama
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
Descripción
Sumario:Mycobacterium tuberculosis truncated hemoglobin, HbN, is endowed with a potent nitric-oxide dioxygenase activity and has been found to relieve nitrosative stress and enhance in vivo survival of a heterologous host, Salmonella enterica Typhimurium, within the macrophages. These findings implicate involvement of HbN in the defense of M. tuberculosis against nitrosative stress. The protein carries a tunnel system composed of a short and a long tunnel branch that has been proposed to facilitate diatomic ligand migration to the heme and an unusual Pre-A motif at the N terminus, which does not contribute significantly to the structural integrity of the protein, as it protrudes out of the compact globin fold. Strikingly, deletion of Pre-A region from the M. tuberculosis HbN drastically reduces its ability to scavenge nitric oxide (NO), whereas its insertion at the N terminus of Pre-A lacking HbN of Mycobacterium smegmatis improved its nitric-oxide dioxygenase activity. Titration of the oxygenated adduct of HbN and its mutants with NO indicated that the stoichiometric oxidation of protein is severalfold slower when the Pre-A region is deleted in HbN. Molecular dynamics simulations show that the excision of Pre-A motif results in distinct changes in the protein dynamics, which cause the gate of the tunnel long branch to be trapped into a closed conformation, thus impeding migration of diatomic ligands toward the heme active site. The present study, thus, unequivocally demonstrates vital function of Pre-A region in NO scavenging and unravels its unique role by which HbN might attain its efficient NO-detoxification ability. © 2009 by The American Society for Biochemistry and Molecular Biology, Inc.

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