Regulation of active site coupling in glutamine-dependent NAD(+) synthetase.
Publication Type:Journal Article
Source:Nat Struct Mol Biol, Volume 16, Issue 4, p.421-9 (2009)
Keywords:Amide Synthases, Ammonia, Catalytic Domain, Crystallography, X-Ray, Glutamine, Kinetics, Models, Molecular, Mycobacterium tuberculosis, NAD, Protein Multimerization, Protein Structure, Quaternary, Protein Subunits
<p>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.</p>