2.A.1.11.3
Inner membrane protein BtsT or YhjX (probably a pyruvate:proton symporter that can also function as an exporter) (Vilhena et al. 2017).  Regulated by Crp as well as the LytS-like histidine sensor kinase, BtsS or YehU, and the corresponding LytTR-like response regulator, BtsR or YehT (Kristoficova et al. 2017).  Possibly induced by peptides as cells enter the stationary growth phase because they release extracellular pyruvate, the true inducer (Kristoficova et al. 2017).  Forms a complex with the BtsT (CsiA; YjiY) transporter (TC# 2.A.114.1.9) and two sensor kinase/response regulator pairs, BtsS/BtsR (YehU/YehT) and YdpA/YdpB, both of which respond to extracellular pyruvate, but with differing affinities (Behr et al. 2014).  The carbon storage regulator A (CsrA) is involved in posttranscriptional regulation of both BtsT (YjiY) and YjiX, a 67 aa soluble protein of unknown function (Behr et al. 2014). 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, have both been given the designation: BtsT (see UniProt entries).