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.
Highlights
The genomic sequence of Rickettsia prowazekii, the obligate intracellular bacterium responsible for epidemic typhus, reveals an uncharacterized invasion gene homolog
Cloning of the Rickettsial invasion gene homolog (invA) Using the polymerase chain reaction, full-length R. prowazekii invA (486 bp) was cloned, and its nucleotide sequence was identical to the published sequence
To determine whether invA homologs are present in other rickettsiae, PCR utilizing R. prowazekii invA gene-specific primers were performed on the genomic DNA of human pathogenic rickettsiae; R. typhi, R. rickettsii, R. akari, and the non-pathogenic Rickettsia species, R. canada and R. rhipicephali
Summary
The genomic sequence of Rickettsia prowazekii, the obligate intracellular bacterium responsible for epidemic typhus, reveals an uncharacterized invasion gene homolog (invA). Alignment analysis of the deduced amino acid sequence of R. prowazekii InvA demonstrated 37– 44% identity to the putative invasion proteins of other invasive bacteria including Bartonella bacilliformis IalA, Neisseria meningitidis putative Ap4A1 pyrophosphatase, Helicobactor pylori InvA, Escherichia coli YgdP, Salmonella typhimurium putative invasion protein, Haemophilus influenzae InvA, and Pseudomonas aeruginosa invasion protein homolog (Fig. 1). Among these homologous genes, only B. bacilliformis ialA and E. coli K1 ygdP have been documented to be associated with host cell invasion [7, 8]. The R. prowazekii invA was Invasion Protein of Rickettsia prowazekii expressed, and the purified protein was characterized to be a member of the dinucleoside pentaphosphate pyrophosphatase subfamily of Nudix hydrolases
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
