title: Cloning and characterization of a bifunctional RelA/SpoT homologue from Mycobacterium tuberculosis.
abstract: A 2.2kb relA/spoT homologue was isolated from Mycobacterium tuberculosis (Mtb) genomic DNA by PCR-amplification. The Mtb gene encodes a protein of 738 amino acid residues, and is flanked upstream by an ORF that is highly similar to the apt gene, and downstream by an ORF that is highly similar to the cypH gene. This dual function Mtb homologue belongs to the relA/spoT family of genes that mediate the stringent response by regulating the synthesis and degradation of guanosine 3',5'-bis(diphosphate) (ppGpp) and pppGpp. In vitro biochemical data indicate that purified RelMtb is a ribosome- and tRNA-independent ATP:GTP/GDP/ITP 3'-pyrophosphoryltransferase. Additionally, purified RelMtb is an Mn2+-dependent, ribosome and tRNA-independent, (p)ppGpp 3'-pyrophosphohydrolase. These reactions were also assessed in vivo in E. coli deleted in both the relA and spoT genes, which generates a (p)ppGpp0 phenotype. RelMtb can suppress this phenotype and can generate more (p)ppGpp than relA in the wild type E. coli control.
authors.affiliation: Division of Infectious Diseases, Department of Medicine, University of Pennsylvania, School of Medicine, Philadelphia, PA 19104, USA.
authors.forename: D
authors.initials: D
authors.lastname: Avarbock
authors.forename: J
authors.initials: J
authors.lastname: Salem
authors.forename: L S
authors.initials: LS
authors.lastname: Li
authors.forename: Z M
authors.initials: ZM
authors.lastname: Wang
authors.forename: H
authors.initials: H
authors.lastname: Rubin
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D017931:DNA Primers; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D008025:Ligases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009169:Mycobacterium tuberculosis / Q000235:genetics*; D011755:Pyrophosphatases / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D017931:DNA Primers; C027627:guanosine-3',5'-bis(diphosphate) 3'-pyrophosphatase; D011755:Pyrophosphatases; D008025:Ligases; C028812:guanosine 3',5'-polyphosphate synthetases