tailieunhanh - Báo cáo khoa học: Cytotoxic activity of nucleoside diphosphate kinase secreted from Mycobacterium tuberculosis

Pathogenicity ofMycobacterium tuberculosisis closely rela-ted to its ability to survive and replicate in the hostile envi-ronment of macrophages. For some pathogenic bacteria, secretion of ATP-utilizing enzymes into the extracellular environment aids in pathogen survival via P2Z receptor-mediated, ATP-induced death of infected macrophages. A component of these enzymes is nucleoside diphosphate kinase (Ndk). Thendkgenewas cloned fromM. tuberculosis H37Rv and expressed inEscherichia coli. | Eur. J. Biochem. 270 625-634 2003 FEBS 2003 doi Cytotoxic activity of nucleoside diphosphate kinase secreted from Mycobacterium tuberculosis B B BB BB X B B B BB BB 1 2 B B B B I B I B BB B B B BB I B 1 3 B B B I B B B I 1 BB B B B B I B MB B B b BB mb B B 1 BB BB I BB I B B MB 4 B B B I B B BB BB B 2 Puneet Chopra Anubha Singh Anil Koul S. Ramachandran Karl Drlica Anil K. Tyagi and Yogendra Singh1 3 1 Institute of Genomics and Integrative Biology Mall Road Delhi India department of Biochemistry South Campus University of Delhi N. Delhi India 3Ambedkar Centre for Biomedical Research University of Delhi India and 4International Center for Public Health NJ USA Pathogenicity of Mycobacterium tuberculosis is closely related to its ability to survive and replicate in the hostile environment of macrophages. For some pathogenic bacteria secretion of ATP-utilizing enzymes into the extracellular environment aids in pathogen survival via P2Z receptor-mediated ATP-induced death of infected macrophages. A component of these enzymes is nucleoside diphosphate kinase Ndk . The ndk gene was cloned from M. tuberculosis H37Rv and expressed in Escherichia coli. Ndk was secreted into the culture medium by M. tuberculosis as determined by enzymatic activity and Western blotting. Purified Ndk enhanced ATP-induced macrophage cell death as assayed by the release of 14C adenine. A catalytic mutant of Ndk failed to enhance ATP-induced macrophage cell death and periodate-oxidized ATP oATP an irreversible inhibitor of P2Z receptor blocked ATP Ndk-induced cell death. Purified Ndk was also found to be autophosphorylated with broad specificity for all nucleotides. Conversion of His117fiGln which is part of the nucleotide-binding site abolished autophosphorylation. Purified Ndk also showed GTPase activity. Collectively these results indicate that secreted Ndk of M. tuberculosis acts as a cytotoxic factor for macrophages which may help in dissemination of the .