title: Structural and dynamic studies on ligand-free adenylate kinase from Mycobacterium tuberculosis revealed a closed conformation that can be related to the reduced catalytic activity.
abstract: Tuberculosis is the leading cause of death worldwide from a single infectious disease. Search of new therapeutic tools requires the discovery and biochemical characterization of new potential targets among the bacterial proteins essential for the survival and virulence. Among them are the nucleoside monophosphate kinases, involved in the nucleotide biosynthesis. In this work, we determined the solution structure of adenylate kinase (AK) from Mycobacterium tuberculosis (AKmt), a protein of 181 residues that was found to be essential for bacterial survival. The structure was calculated by a simulated annealing protocol and energy minimization using experimental restraints, collected by nuclear magnetic resonance spectroscopy. The final, well-defined 20 NMR structures show an average root-mean-square deviation of 0.77 A for the backbone atoms in regular secondary structure segments. The protein has a central CORE domain, composed of a five-stranded parallel beta-sheet surrounded by seven alpha-helices, and two peripheral domains, AMPbd and LID. As compared to other crystallographic structures of free form AKs, AKmt is more compact, with the AMP(bd) domain closer to the CORE of the protein. Analysis of the (15)N relaxation data enabled us to obtain the global rotational correlation time (9.19 ns) and the generalized order parameters (S(2)) of amide vectors along the polypeptide sequence. The protein exhibits restricted movements on a picosecond to nanosecond time scale in the secondary structural regions with amplitudes characterized by an average S(2)() value of 0.87. The loops beta1/alpha1, beta2/alpha2, alpha2/alpha3, alpha3/alpha4, alpha4/beta3, beta3/alpha5, alpha6/alpha7 (LID), alpha7/alpha8, and beta5/alpha9 exhibit rapid fluctuations with enhanced amplitudes. These structural and dynamic features of AKmt may be related to its low catalytic activity that is 10-fold lower than in their eukaryote counterparts.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale U350 et Institut Curie-Recherche, Centre Universitaire, Bâtiments 110-112, F-91405 Orsay, France. Simona.Burlacu@curie.u-psud.fr
authors.forename: Simona
authors.initials: S
authors.lastname: Miron
authors.forename: Hélène
authors.initials: H
authors.lastname: Munier-Lehmann
authors.forename: Constantin T
authors.initials: CT
authors.lastname: Craescu
mesh_terms: D000263:Adenylate Kinase / Q000737:chemistry*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D002384:Catalysis; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D019906:Nuclear Magnetic Resonance, Biomolecular; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D008024:Ligands; D011994:Recombinant Proteins; D000263:Adenylate Kinase