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)