TauBC

TauBC refers to a two-subunit membrane protein complex that forms part of the high-affinity taurine uptake system in many bacteria. In most organisms, TauB and TauC function as the transmembrane components of an ATP-binding cassette (ABC) transporter; they cooperate with a periplasmic binding protein TauA and an ATPase subunit to import taurine (2-aminoethanesulfonate) and related sulfonates from the periplasm into the cytoplasm.

TauB is predicted to consist of multiple transmembrane helices and contributes to the substrate translocation pathway; TauC also contributes to the transmembrane core and influences substrate specificity and coupling with the ATPase. The two subunits work together to form the channel through which taurine passes during transport.

Transport mechanism typically involves TauA binding taurine in the periplasm and delivering it to the TauBC complex. ATP hydrolysis by the cognate ATPase provides the energy that drives conformational changes within TauB and TauC, enabling translocation of taurine across the inner membrane and into the cytoplasm.

Genetics and regulation of TauBC are commonly linked to the tau gene cluster. TauABC components are often co-transcribed, or arranged adjacently, with expression commonly induced in the presence of taurine. Regulatory systems can vary by species, with TauR-like regulators reported in some bacteria.

Distribution and significance: the TauBC components are widely distributed among Gram-negative bacteria and play a key role in utilizing taurine as a sulfur source and, in some contexts, as an electron donor under anaerobic conditions. They are of interest for understanding microbial sulfur metabolism and the metabolic capabilities of gut microbiota. See also: taurine, ABC transporters, periplasmic binding proteins.