Abstract
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.
Publication types
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Amino Acid Transport Systems / chemistry
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Amino Acid Transport Systems / classification
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Amino Acid Transport Systems / genetics*
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Amino Acid Transport Systems / metabolism
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Amino Acid Transport Systems, Neutral*
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Amino Acids / metabolism
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Animals
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Archaea / genetics*
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Archaea / metabolism
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Bacteria / genetics*
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Bacteria / metabolism
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Bacterial Proteins*
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Carrier Proteins / chemistry
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Carrier Proteins / classification
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Carrier Proteins / genetics*
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Carrier Proteins / metabolism
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Computational Biology / methods
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Gene Duplication
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Humans
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Membrane Proteins / chemistry
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Membrane Proteins / classification
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Membrane Proteins / genetics*
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Membrane Proteins / metabolism
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Molecular Sequence Data
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Phylogeny
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RNA, Ribosomal, 16S / genetics
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Sequence Alignment
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Sequence Homology, Amino Acid
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Yeasts / genetics*
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Yeasts / metabolism
Substances
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Amino Acid Transport Systems
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Amino Acid Transport Systems, Neutral
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Amino Acids
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Bacterial Proteins
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Carrier Proteins
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Membrane Proteins
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RNA, Ribosomal, 16S
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ThrE protein, Corynebacterium glutamicum