2.A.114.1.9
High affinity (Km 16 mμM) pyruvate:H⁺ symporter, BtsT (from "Brenztraubensaure", the German word for pyruvate), also called YjiY of 716 aas and 16 - 18 TMSs (Kristoficova et al. 2017). If 16 TMSs, they occur in a 2 + 2 + 5 + 2 (space) +1 + 3 + 1 TMS arrangement, or if 18 TMSs, there are two additional TMSs between the first11 TMSs and the last 5 TMSs. Regulated by Crp as well as the LytS-like histidine sensor kinase, BtsS (YehU) which senses extracellular pyruvate, and it functions with the corresponding LytTR-like response regulator, BtsR (YehT).  Although the true inducer is extracellular pyruvate as noted above, it is induced by peptides as cells enter the stationary growth phase, presumably because pyruvate is released from these peptides (Kraxenberger et al. 2012).  BtsT forms a complex with the MFS transporter, YhjX (TC# 2.A.1.11.3) and two sensor kinase/response regulator pairs, YehU/YehT and YdpA/YdpB (Behr et al. 2014).  Both transporters are also posttranscriptionally regulated by CsrA (Behr et al. 2014).  The LytS-type histidine kinase, BtsS, is a 7-transmembrane receptor that binds pyruvate (Qiu et al. 2023). The two proteins, YhjX (TC# 2.A.1.11.3) and YjiY (TC# 2.A.114.1.9) may function together as an oligomer, and confusingly, both have been given the same designation: BtsT (see UniProt entries).