Evolution of the prokaryotic protein translocation complex: a comparison of archaeal and bacterial versions of SecDF.
Protein translocation across the prokaryotic plasma membrane occurs at the translocon, an evolutionarily conserved membrane-embedded proteinaceous complex. Together with the core components SecYE, prokaryotic translocons also contain auxilliary proteins, such as SecDF. Alignment of bacterial and archaeal SecDF protein sequences reveals the presence of a similar number of homologous regions within each protein. Moreover, the conserved sequence domains in the archaeal proteins are located in similar positions as their bacterial counterparts. When these domains are, however, compared along Bacteria-Archaea lines, a much lower degree of similarity is detected. In Bacteria, SecDF are thought to modulate the membrane association of SecA, the ATPase that provides the driving force for bacterial protein secretion. As no archaeal version of SecA has been detected, the sequence differences reported here may reflect functional differences between bacterial and archaeal SecDF proteins, and by extension, between the bacterial and archaeal protein translocation processes. Moreover, the apparent absence of SecDF in several completed archaeal genomes suggests that differences may exist in the process of protein translocation within the archaeal domain itself.
Department of Life Sciences, Ben Gurion University, P.O. Box 653, Beersheva 84105, Israel. jeichler@bgumail.bgu.ac.il
Jerry
J
Eichler
D001105:Archaea / Q000235:genetics*; D001419:Bacteria / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D019143:Evolution, Molecular; D008565:Membrane Proteins / Q000235:genetics*; D026901:Membrane Transport Proteins / Q000235:genetics*; D010802:Phylogeny; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D001426:Bacterial Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C075767:secD protein, Bacteria; C075768:secF protein, Bacteria