THE TWIN-ARGININE TRANSLOCATION PATHWAY IN THE OBLIGATE ANAEROBE DESULFITOBACTERIUM
The genus Desulfitobacterium belong to the low-GC gram-positive phylogenic group and is a versatile obligate anaerobe capable of reducing very diverse terminal electron acceptors such as sulfite, nitrate, fumarate, thiosulfate, and a few polluting chlorinated compounds in a environmental-friendly energy metabolism called dehalorespiration. Analysis of available desulfitobacteria genomes revealed on one hand a high number of predicted proteins that are translocated in a folded conformation to or across the cytoplasmic membrane by the twin-arginine translocation (Tat) pathway. On the other hand a striking redundancy in the pore-forming protein (TatA) of the Tat translocase was observed. It might reflect the strong need for the translocase, and/or some TatA specificity of the Tat-dependent translocated proteins. The presence of numerous Tat-dependent oxidoreductases, for most of which the substrate specificity is not yet known, correlates well with the high versatility of anaerobic respiration of this genus. Half of Tat-dependent proteins in Desulfitobacterium belong also to the class of lipoproteins that might keep them attached to the cytoplasmic membrane. The functional characterization of the Tat system in our model organism Desulfitobacterium hafniense strain TCE1 is under progress.