Evolution of the Translocation and Assembly Module (TAM).
Bottom Line: Bacterial outer membrane proteins require the beta-barrel assembly machinery (BAM) for their correct folding and function.An additional feature of the BAM is the translocation and assembly module (TAM), comprised TamA (an Omp85 family protein) and TamB.Several sequence characteristics were discovered to define the TamB protein family: A signal-anchor linkage to the inner membrane, beta-helical structure, conserved domain architecture and a C-terminal region that mimics outer membrane protein beta-strands.
Affiliation: Department of Microbiology, Monash University, Melbourne, Victoria, Australia.Show MeSH
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Mentions: The protein sequences defined as TamB show a relatively consistent length profile, with only few exceptions of very long length (supplementary fig. S3, Supplementary Material online). A characteristic feature of these sequences is a C-terminally located DUF490 domain (fig. 3 and supplementary fig. S4, Supplementary Material online). Those sequences classified as TamB, but with no Pfam-defined domains recognized with the given cutoff (fig. 3), have predicted secondary structure features that suggest a conserved structure (fig. 3). In E. coli, the DUF490 domain corresponds to a 37-kDa region within TamB (residues 914–1,259), and the number of residues in the DUF490 domains in other TamB sequences is relatively conserved. In contrast, AsmA proteins show more diversity regarding sequence length (supplementary fig. S3, Supplementary Material online), and the AsmA domain covers either the entire protein or only the N-terminal region (supplementary fig. S4, Supplementary Material online).Fig. 3.—
Affiliation: Department of Microbiology, Monash University, Melbourne, Victoria, Australia.