2Graduate School, Chinese Academy of Science, Beijing 100039, China
3Department of Molecular Microbiology and Immunology, School of Hygiene and Public Health, Johns Hopkins University, Baltimore, MD 21205, USA
* To whom correspondence should be addressed.
Received December 30, 2008; Revision received January 25, 2009
Sir2 family proteins are highly conserved and catalyze a well-characterized NAD-dependent protein deacetylation reaction that regulates multiple cellular processes including aging, gene silencing, cellular differentiation, and metabolic pathways. Little is known about Sir2 family proteins in bacteria. The Sir2 homolog Rv1151c of Mycobacterium tuberculosis was cloned and over-expressed in Escherichia coli, and the protein then purified by Ni2+-affinity chromatography to homogeneity. The purified recombinant protein showed a typical NAD-dependent protein deacetylase activity that could be inhibited by nicotinamide and other known Sir2 inhibitors. The optimal temperature and pH for activity of Rv1151c are 25°C and pH 9 ± 1, respectively. Rv1151c is capable of deacetylating the acetyl-CoA synthetase from M. tuberculosis. However, unlike Sir2 family proteins identified from other bacteria, Rv1151c shows a substrate-independent NAD glycohydrolase activity in accordance with its auto-ADP ribosylation activity.
KEY WORDS: ADP-ribosyltransferase, deacetylase, Mycobacterium tuberculosis, NAD glycohydrolase, Sir2