title: Regulation of active site coupling in glutamine-dependent NAD(+) synthetase.
abstract: NAD(+) is an essential metabolite both as a cofactor in energy metabolism and redox homeostasis and as a regulator of cellular processes. In contrast to humans, Mycobacterium tuberculosis NAD(+) biosynthesis is absolutely dependent on the activity of a multifunctional glutamine-dependent NAD(+) synthetase, which catalyzes the ATP-dependent formation of NAD(+) at the synthetase domain using ammonia derived from L-glutamine in the glutaminase domain. Here we report the kinetics and structural characterization of M. tuberculosis NAD(+) synthetase. The kinetics data strongly suggest tightly coupled regulation of the catalytic activities. The structure, the first of a glutamine-dependent NAD(+) synthetase, reveals a homooctameric subunit organization suggesting a tight dependence of catalysis on the quaternary structure, a 40-A intersubunit ammonia tunnel and structural elements that may be involved in the transfer of information between catalytic sites.
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742-2021, USA. nlaronde@umd.edu
authors.forename: Nicole
authors.initials: N
authors.lastname: LaRonde-LeBlanc
authors.forename: Melissa
authors.initials: M
authors.lastname: Resto
authors.forename: Barbara
authors.initials: B
authors.lastname: Gerratana
mesh_terms: D019732:Amide Synthases / Q000737:chemistry*; D000641:Ammonia / Q000378:metabolism; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D005973:Glutamine / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D055503:Protein Multimerization; D020836:Protein Structure, Quaternary; D021122:Protein Subunits
chemical_list: D021122:Protein Subunits; D005973:Glutamine; D009243:NAD; D000641:Ammonia; D019732:Amide Synthases; C038479:NAD+ synthase