A GENOMIC AND FUNCTIONAL APPRAISAL OF TWIN-ARGININE TRANSLOCATION PATHWAY SYSTEM IN Anaplasma marginale

NUÑEZ P.; MORETTA R.; SORIA M.; FARBER M.

Buenos Aires

Conferencia; International Conference on Ticks and Tick-borne Pathogens; 2008

The Twin arginine translocation pathway is a novel protein transport system that targets folded proteins across the inner membrane of bacteria. Particularly, protein export and translocation systems acquire great relevance as they are implicated in bacterial virulence mechanisms. The integral membrane proteins tatA, B and C are essential components of system. While tat components have been identified in most of the sequenced bacterial genomes the extent to which this secretory pathway is utilized in bacteria is not well characterized. Our previous work using an alkaline phosphatase gene (phoa) fusion library of A. Marginale, for the selection of sequence coding for exported products, led us to the identification of tatA subunit. Notably, despite the fact that tatB and C were annotated in A. maginale genome, tatA gene had been omitted in the annotation process. Comparative genomic analysis throughout 23 alphaproteobacteria genomes confirmed the presence of the three genes in almost all studied genomes. Analyzing the synteny of the tatA, B, and C genes, it was possible to split the class into two groups, one with tatABC operon and another one with an scattered structure. Using A. marginale RNA RT-PCR and qRT-PCR assays were performed to demonstrate the expression and determine stoichiometric ratio of tat components so as to characterize transcriptional regulation mechanism. The ability of A. marginale tatA gene to compensate for the absence of the cognate E. coli one was attained, strengthening the hypothesis of a functional TAT system in A. marginale. Finally, a genome?wide identification of putative tat substrates among alphaproteobacteria was performed using TatFIND1.4 algorithm. Since some organisms appear to make extensive use of this pathway, others such as A. marginale, seems to secrete very few products through it. Gene ontology and clustering analysis led to the classification of the organism into groups regarding to the properties and/or number of predicted substrates. Whether or not this classification could be in accordance to adaptive mechanism for very different ecological niches will be discussed.