The ubiquitous ThrE family of putative transmembrane amino acid efflux transporters.
We here report sequence analyses of a newly described family of putative amino acid exporters, the ThrE family. Homologues were identified in select bacteria, archaea and eukaryotes, but only in the fungal kingdom of eukaryotes. These proteins can exist either as single polypeptide chains or as pairs of polypeptide chains. Computational evidence suggests that these proteins exhibit 10 transmembrane alpha-helical segments (TMSs), having arisen from a five TMS precursor by an early intragenic duplication event. The phylogenetic tree of the ThrE family reveals that most proteins cluster according to organismal phylogeny with only a few exceptions, suggesting that the former proteins are orthologues. All family members exhibit hydrophilic N-terminal (and occasional C-terminal) extensions that show limited sequence similarity with a domain of unknown function found in many peptidases and proteases. The significance of these observations is discussed.
Yen
Ming-Ren
MR
Department of Biology, University of California at San Diego, La Jolla 92093-0116, USA.
Tseng
Yi-Hsiung
YH
Simic
Petra
P
Sahm
Hermann
H
Eggeling
Lothar
L
Saier
Milton H
MH
D000595:Amino Acid Sequence; D026905:Amino Acid Transport Systems / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001105:Archaea / Q000235:genetics* / Q000378:metabolism; D001419:Bacteria / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D019295:Computational Biology / Q000379:methods; D020440:Gene Duplication; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015003:Yeasts / Q000235:genetics* / Q000378:metabolism
D026905:Amino Acid Transport Systems; D026921:Amino Acid Transport Systems, Neutral; D000596:Amino Acids; D001426:Bacterial Proteins; D002352:Carrier Proteins; D008565:Membrane Proteins; D012336:RNA, Ribosomal, 16S; C435513:ThrE protein, Corynebacterium glutamicum