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)



Anantharaman, V., L.M. Iyer, and L. Aravind. (2012). Ter-dependent stress response systems: novel pathways related to metal sensing, production of a nucleoside-like metabolite, and DNA-processing. Mol Biosyst 8: 3142-3165.

Burian, J., N. Tu, L. Kl'ucár, L. Guller, G. Lloyd-Jones, S. Stuchlík, P. Fejdi, P. Siekel, and J. Turna. (1998). In vivo and in vitro cloning and phenotype characterization of tellurite resistance determinant conferred by plasmid pTE53 of a clinical isolate of Escherichia coli. Folia Microbiol (Praha) 43: 589-599.

Huang, Y., K. Mu, X. Teng, Y. Zhao, Y. Funato, H. Miki, W. Zhu, Z. Xu, and M. Hattori. (2021). Identification and mechanistic analysis of an inhibitor of the CorC Mg transporter. iScience 24: 102370.

Kazanov, M.D., A.G. Vitreschak, and M.S. Gelfand. (2007). Abundance and functional diversity of riboswitches in microbial communities. BMC Genomics 8: 347.

Kormutakova, R., L. Klucar, and J. Turna. (2000). DNA sequence analysis of the tellurite-resistance determinant from clinical strain of Escherichia coli and identification of essential genes. Biometals 13: 135-139.

Kwon, K.C. and M.H. Cho. (2008). Deletion of the chloroplast-localized AtTerC gene product in Arabidopsis thaliana leads to loss of the thylakoid membrane and to seedling lethality. Plant J. 55: 428-442.

Meyer, M.M., M.C. Hammond, Y. Salinas, A. Roth, N. Sudarsan, and R.R. Breaker. (2011). Challenges of ligand identification for riboswitch candidates. RNA Biol 8: 5-10.

Orth, D., K. Grif, M.P. Dierich, and R. Würzner. (2007). Variability in tellurite resistance and the ter gene cluster among Shiga toxin-producing Escherichia coli isolated from humans, animals and food. Res. Microbiol. 158: 105-111.

Sharma, R. and T.V. Mishanina. (2023). A riboswitch-controlled manganese exporter (Alx) tunes intracellular Mn concentration in at alkaline pH. bioRxiv.

Stancik, L.M., D.M. Stancik, B. Schmidt, D.M. Barnhart, Y.N. Yoncheva, and J.L. Slonczewski. (2002). pH-dependent expression of periplasmic proteins and amino acid catabolism in Escherichia coli. J. Bacteriol. 184: 4246-4258.

Turkovicova, L., R. Smidak, G. Jung, J. Turna, G. Lubec, and J. Aradska. (2016). Proteomic analysis of the TerC interactome: Novel links to tellurite resistance and pathogenicity. J Proteomics. [Epub: Ahead of Print]


TC#NameOrganismal TypeExample

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. 2007Meyer 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


TC#NameOrganismal TypeExample

TerC homologue


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


TC#NameOrganismal TypeExample

DUF475; PRK14013 protein (341 aas; 9 TMSs)


DUF475 protein of Methanocaldococcus vulcanius (C9RH03)


TC#NameOrganismal TypeExample

TC#NameOrganismal TypeExample