TatB

TatB is a component of the bacterial twin-arginine translocation (Tat) pathway, a system used to move folded proteins across the cytoplasmic membrane. Along with TatA and TatC, TatB forms part of the machinery that recognizes, binds, and guides substrates bearing twin-arginine signal peptides to the translocase.

TatB is a small integral membrane protein characterized by a single transmembrane helix near the N-terminus, with the remaining sequence contributing to amphipathic regions that interact with other Tat components. This architecture enables TatB to sit in the inner membrane and participate in protein–protein interactions necessary for substrate recognition and complex assembly.

Functionally, TatB participates in forming the TatBC receptor complex with TatC. It helps recognize substrates containing the twin-arginine motif in their signal peptides and assists in recruiting TatA to the receptor, aiding the assembly of the translocation apparatus. The translocation process transports fully folded proteins, in contrast to Sec pathways that move unfolded polypeptides.

Genetically, tatB is typically encoded in the tatABC operon and expressed in coordination with tatA and tatC. Disruption of tatB often compromises the Tat pathway, leading to defective export of many Tat substrates, though some proteins may be exported at reduced efficiency in certain organisms.

In research and biotechnology, the Tat pathway, including TatB, is of interest for the secretion of folded recombinant proteins into the periplasm or extracellular milieu, leveraging the pathway’s ability to handle properly folded substrates. See also: twin-arginine translocation pathway, TatA, TatC.