2.A.114 The Peptide Transporter Carbon Starvation CstA (CstA) Family
The CstA family consists of proteins from bacteria, and archaea. These proteins are of various sizes and topologies. For example, CstA of E. coli has 701 aas with 18 putative TMSs. It has a long N-terminal CstA domain and a short C-terminal DUF4161 domain. This protein is encoded by a carbon starvation inducible gene cstA that is under cyclic AMP-CRP control. Circumstantial evidence suggested that it may be a peptide transporter (Schultz and Matin, 1991). A Campylobacter jejuni homologue has been shown to transport di- and tripeptides (see TC# 2.A.114.1.5) (Rasmussen et al., 2013).
Carbon starvation inducible protein CstA (701 aas; 18 TMSs). This protein has been shown to be a pyruvate uptake system, working together with a small protein of 65 aas, YbdD (Hwang et al. 2018). It may also transport peptides.
Bacteria and Archaea
CstA of E. coli (P15078)
BtsT (from the German word for pyruvate: """"Brenztraubensäure"""" transporter) or YjiY of 716 aas and 18 TMSs. It is a high affinity (Km + 16 μM), inducible, specific pyruvate:proton uptake symporter (Kristoficova et al. 2017). Expression of the btsT (yjiY) gene is regulated by the LytS-like histidine kinase, BtsS, a sensor of extracellular pyruvate, together with the LytTR-like response regulator, BtsR (Kristoficova et al. 2017).It may also mediate uptake of specific peptides, thus initiating their metabolism, but this has not been demonstrated directly. It indirectly influences flagellar biosynthesis and virulence. BtsT (YjiY) is required for successful colonization of Salmonella in the mouse gut (Garai et al. 2015). It also influences expression of the mgtC gene to regulate biofilm formation (Garai et al. 2017).
YjiY of Salmonella enterica; subspecies Typhimurium (strain LT2)
Carbon starvation protein, CstA (484 aas; 13 TMSs).
CstA of Anaerococcus prevotii (C7RGN6)
CstA (579 aas; 15 TMSs)
CstA of Thermococcus kodakaraensis (Q5JIF7)
CstA of 483 aas with 12 or 13 putative TMSs.
CstA of Chlostridium perfringens (Q8XME6)
CstA of 703 aas and 18 putative TMSs. In C. jejuni, this protein plays a role in starvation responses and peptide uptake. A ΔcstA mutant has reduced use of di- and tri-peptides when used as nitrogen sources. The mutant also has reduced motility and agglutination and shows decreased host-pathogen relationships (Rasmussen et al. 2013).
CstA of Campylobacter jejuni (Q0P9Y2)
CstA of 511 aas and 14 putative TMSs in a possible 10 4 arrangement. The last 4 TMSs correspond to the DUF4161 domain in CDD.
CstA of Fibrobacter succinogenes
CstA of 791 aas and 16 TMSs in an apparent 11 + 5 + 1 arrangement.
CstA of Bifidobacterium animalis
CstA of 704 aas and 16 TMSs in a 4 + 6 + 6 arrangement.
CstA of Singulisphaera acidiphila
High affinity (Km 16 mμM) pyruvate:H+ symporter, BtsT (from "Brenztraubensaure", the German word for pyruvate), formerly YjiY of 716 aas and 16 - 18 TMSs (Kristoficova et al. 2017). Regulated by Crp as well as the LytS-like histidine sensor kinase, BtsS (YehU) which senses extracellular pyruvate, and 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).
BtsT or YjiY of E. coli