2.A.79 The Threonine/Serine Exporter (ThrE) Family

A single member of the ThrE family has been characterized: the ThrE protein of Corynebacterium glutamicum (Simic et al., 2002). This protein (489aas) exhibits 10 putative TMSs and catalyzes the pmf-dependent efflux of threonine and serine (Kruse et al., 2002). It has close homologues in Mycobacterium tuberculosis (Rv 3737; 529aas; pirB70798) and Strepomyces coelicolor (578aas; pirT36336. However more distant homologues, some of which consist of 'spliced' two-component systems, are also found in E. coli, Vibrio cholera, Xylella fastidiosa, Saccharomyces cerevisiae, Schizosaccharomyces pombe and Methanobacterium thermoautotrophicum. Thus, members of the ThrE family are diverse in sequence and are ubiquitous, being found in bacteria, archaea and eukaryotes (Eggeling and Sahm, 2003; Yen et al., 2002).

The transport reaction catalyzed by ThrE is:

threonine or serine (in) + H+ (out) ⇌ threonine or serine (out) + H+ (in)

This family belongs to the .



Bendezú, F.O. and P.A. de Boer. (2008). Conditional lethality, division defects, membrane involution, and endocytosis in mre and mrd shape mutants of Escherichia coli. J. Bacteriol. 190: 1792-1811.

Eggeling, L. and H. Sahm. (2003). New ubiquitous translocators: amino acid export by Corynebacterium glutamicum and Escherichia coli. Arch. Microbiol. 180: 155-160.

Kruse, D., R. Krämer, L. Eggeling, M. Rieping, W. Pfefferle, J.H. Tchieu, Y.J. Chung, M.H. Jr Saier, and A. Burkovski. (2002). Influence of threonine exporters on threonine production in Escherichia coli. Appl. Microbiol. Biotechnol. 59: 205-210.

Leaver, M. and J. Errington. (2005). Roles for MreC and MreD proteins in helical growth of the cylindrical cell wall in Bacillus subtilis. Mol. Microbiol. 57: 1196-1209.

Simic, P., J. Willuhn, H. Sahm, and L. Eggeling. (2002). Identification of glyA (encoding serine hydroxymethyltransferase) and its use together with the exporter ThrE to increase L-threonine accumulation by Corynebacterium glutamicum. Appl. Environ. Microbiol. 68: 3321-3327.

Southworth, T.W., A.A. Guffanti, A. Moir, and T.A. Krulwich. (2001). GerN, an endospore germination protein of Bacillus cereus, is an Na+/H+-K+ antiporter. J. Bacteriol. 183: 5896-5903.

Stratmann, T., S. Madhusudan, and K. Schnetz. (2008). Regulation of the yjjQ-bglJ operon, encoding LuxR-type transcription factors, and the divergent yjjP gene by H-NS and LeuO. J. Bacteriol. 190: 926-935.

Yen, M.R., Y.H. Tseng, P. Simic, H. Sahm, L. Eggeling, and M.H. Saier, Jr. (2002). The ubiquitous ThrE family of putative transmembrane amino acid efflux transporters. Res. Microbiol. 153: 19-25.


TC#NameOrganismal TypeExample

Threonine/Serine exporter, ThrE (10 TMSs; DUF1212; Eggeling & Sahm, 2003)

Bacteria, archaea and eukarya

ThrE of Corynebacterium glutamicum (Q79VD1)


Pheromone-regulated membrane protein 10 of 1150 aas and 10 - 12 TMSs.  CDD shows YjjP (DUF1212) and ProP (MFS) domains overlapping in the C-terminal transmembrane region.  The N-terminal soluble domains shows sequence similarity to Insecticidal Vegetative Protein-3 Family (TC# 1.C.105.2.7; e-8).

Pheromone-regulated protein 10 of Candida albicans (Yeast)


ThrE homologue


ThrE homologue of Myxococcus xanthus


ThrE homologue


ThrE homologue of Propionibacterium acnes


PF06738 family protein


PF06738 family protein of Fusobacterium nucleatum


Putative 2-component glycine/alanine porter


Putative gly/ala porter of Treponema denticola


Uncharacterized protein of 147 aas and 5 TMSs.

UP of Clostridium clariflavum


Uncharacterized protein of 142 aas

UP of Paenibacillus sp. FSL H8-237


Uncharacterized protein of 430 aas and 10 TMSs in a 5 + 5 spatial arrangement.

UP of Mobilicoccus pelagius


Uncharacterized protein of 606 aas and 9 or 10 TMSs

UP of Mucor circinelloides (Mucormycosis agent) (Calyptromyces circinelloides)


TC#NameOrganismal TypeExample

Protein of unknown function, YjjP (5TMSs; DUF1212). Regulated by H-NS (Stratmann et al. 2008).


YjjP of E.coli (Q8FA71)


DUF1212 homologue


DUF1212 homologue of Rhodopseudomonas palustris


TC#NameOrganismal TypeExample