The RdhT protein family: chaperoning bacterial organohalide respiration
Organohalide respiration (OHR) is a bacterial anaerobic energy metabolism that uses many chlorinated organic compounds as terminal electron donors. The process is catalyzed by a class of complex redox enzymes called reductive dehalogenases which harbour a corrinoid and two FeS clusters as cofactors and which are transported across the cytoplasmic membrane via the Twin-arginine translocation (Tat) pathway. The PceT protein is encoded in the conserved pceABCT gene cluster supporting OHR with tetrachloroethene as electron acceptor. More generally RdhT encoding genes were found in several (sometimes only presumably) OH-respiring bacteria such as Dehalobacter, Desulfitobacterium, Geobacter and Shewanella. The RdhT family shows striking sequence homology with the Trigger Factor, the general chaperone, but lacks the N-terminal ribosome-binding domain. We present here a first in vivo study of the function of PceT from Desulfitobacterium using heterologous functional complementation in E. coli, together with the analysis of the two full-length and apparently redundant TFs commonly present in Desulfitobacteria. We demonstrated that all three TF chaperones were functional in vivo, as judged by their ability to partially suppress bacterial growth defect and protein aggregation in the absence of two major E. coli chaperones, namely TF and DnaK. Next, we found that the N-terminal truncated TF-like protein PceT functions as a dedicated chaperone for the cognate reductive dehalogenase PceA by solubilizing and stabilizing the redox enzyme in the heterologous system. Preliminary data suggest that PceT interacts with the Tat signal peptide of PceA and therefore represents as a paradigmatic member of the RdhT family a new class of TF-like chaperones involved in the maturation of redox proteins secreted by the Tat pathway.
Record created on 2011-05-20, modified on 2016-08-09