title: The Rickettsia prowazekii invasion gene homolog (invA) encodes a Nudix hydrolase active on adenosine (5')-pentaphospho-(5')-adenosine.
abstract: The genomic sequence of Rickettsia prowazekii, the obligate intracellular bacterium responsible for epidemic typhus, reveals an uncharacterized invasion gene homolog (invA). The deduced protein of 18,752 Da contains a Nudix signature, the specific motif found in the Nudix hydrolase family. To characterize the function of InvA, the gene was cloned and overexpressed in Escherichia coli. The expressed protein was purified to near homogeneity and subsequently tested for its enzymatic activity against a series of nucleoside diphosphate derivatives. The purified InvA exhibits hydrolytic activity toward dinucleoside oligophosphates (Np(n)N; n > or = 5), a group of cellular signaling molecules. At optimal pH 8.5, the enzyme actively degrades adenosine (5')-pentaphospho-(5')-adenosine into ATP and ADP with a K(m) of 0.1 mM and k(cat) of 1.9 s(-1). Guanosine (5')-pentaphospho-(5')-guanosine and adenosine-(5')-hexaphospho (5')-adenosine are also substrates. Similar to other Nudix hydrolases, InvA requires a divalent metal cation, Mg(2+) or Zn(2+), for optimal activity. These data suggest that the rickettsial invasion protein likely plays a role in controlling the concentration of stress-induced dinucleoside oligophosphates following bacterial invasion.
authors.affiliation: Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore, Maryland 21201, USA.
authors.forename: Jariyanart
authors.initials: J
authors.lastname: Gaywee
authors.forename: WenLian
authors.initials: W
authors.lastname: Xu
authors.forename: Suzana
authors.initials: S
authors.lastname: Radulovic
authors.forename: Maurice J
authors.initials: MJ
authors.lastname: Bessman
authors.forename: Abdu F
authors.initials: AF
authors.lastname: Azad
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D015226:Dinucleoside Phosphates / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D007700:Kinetics; D008969:Molecular Sequence Data; D020543:Proteome / Q000235:genetics / Q000378:metabolism; D011755:Pyrophosphatases / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012283:Rickettsia prowazekii / Q000201:enzymology* / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D000096964:Nudix Hydrolases
chemical_list: D001426:Bacterial Proteins; D015226:Dinucleoside Phosphates; D020543:Proteome; D011755:Pyrophosphatases; D011994:Recombinant Proteins; D000096964:Nudix Hydrolases; C075518:invA protein, Bacteria; C012275:P(1),P(5)-di(adenosine-5'-)pentaphosphate