2.A.109 The Tellurium Ion Resistance (TerC) Family
The TerC family (Pfam 03741) includes the E. coli TerC protein which has been implicated in tellurium resistance (Burian et al. 1998). It is hypothesized to catalyze efflux of tellurium ions (Burian et al., 1998; Kormutakova et al. 2000). TerC is encoded by plasmid pTE53 from a clinical isolate of E. coli (Burian et al., 1998). It has 346 aas and 9 putative TMSs with a large hydrophilic loop between TMSs 5 and 6. A homologue in Arabidopsis thaliana (TC# 9.A.30.2.1) may function in prothylakoid membrane biogenises during early chloroplast development (Kwon and Cho 2008). It has 384 aas and 7-8 putative TMSs. In E. coli, TerC forms a membrane complex with TerB as well as DctA, PspA, HslU, and RplK. The TerB/TerC complex may link different functional modules with biochemical activities of C4-dicarboxylate transport, inner membrane stress response (phage shock protein regulatory complex), ATPase/chaperone activity, and proteosynthesis (Turkovicova et al. 2016). It may be part of a metal sensing stress response system (Anantharaman et al. 2012). The co-presence of TerC and TerE but not TerF correlates with tellurite resistance when several hundred bacterial strains were assayed (Orth et al. 2007). Some of these proteins have C-terminal CBS domains.
The reaction proposed to be catalyzed by TerC is:
Tellurium ions (in) → tellurium ions (out)
Tellurium resistance protein, TerC. Interactions with several other proteins including TerB have been demonstrated (Turkovicova et al. 2016).
TerC of E. coli (CAB42997)
Alx protein (9-10 TMSs)
Alx of Neisseria meningitidis (F0N2E7)
YceF (262 aas; 7 TMSs)
YceF of Bacillus cereus (B5UIP4)
Putative transporter, YkoY (8TMSs) (Kazanov et al. 2007; Meyer et al. 2011)
YkoY of Bacillus subtilis (O34997)
TerC family efflux pump
TerC family member of Sinorhizobium fredii
Uncharacterized protein of 352 aas
UP of Brachypodium distachyon (Purple false brome) (Trachynia distachya)
Membrane protein induced over 100x by alkaline conditions, Alx or YgjT of 321 aas and 9 TMSs (Stancik et al. 2002). This riboswitch-controlled manganese exporter (Alx) tunes intracellular Mn2+ concentration in E. coli at alkaline pH. A set of acidic residues in the predicted TMSs of Alx play a role in Mn2+ export (Sharma and Mishanina 2023).
YgjT or Alx of E. coli
TerC homologue of Rhodopirellula baltica
Hypothetical protein of 300 aas and 7 putative TMSs
HP of Rhodopirellula baltica
8 TMS membrane protein including a transmembrane domain homologous to other proteins in the TerC family (2.A.109) with the transmembrane domain having a 4 + 4 TMS arrangement, and a C-terminal domain (residues 622 - 889) with high sequence identity with hemolysin C and all members of the HlyC family (TC# 1.C.126), including some Mg2+ exporters in Cyclin M Mg2+ Exporter (CNNM) (TC family 1.A.112). The hydrophilic N-terminal CBS domain is an integrase domain but may bind ATP (Huang et al. 2021).
Membrane protein of E. coli
DUF475; PRK14013 protein (341 aas; 9 TMSs)
DUF475 protein of Methanocaldococcus vulcanius (C9RH03)