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Alpha coat protein COPA (HEP‐COP): presence of an Alu repeat in cDNA and identity of the amino terminus to xenin
Author(s) -
CHOW V. T. K.,
QUEK H. H.
Publication year - 1997
Publication title -
annals of human genetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.537
H-Index - 77
eISSN - 1469-1809
pISSN - 0003-4800
DOI - 10.1046/j.1469-1809.1997.6140369.x
Subject(s) - biology , peptide sequence , microbiology and biotechnology , complementary dna , amino acid , conserved sequence , biochemistry , gene
We previously sequenced the 4333‐nucleotide cDNA of the COPA (HEP‐COP) gene which encodes the human homologue of the α‐subunit of the coatomer protein complex, involved in intracellular protein transport. Within the 3′ untranslated region at nucleotides 4049–4333 was observed an Alu repeat containing conserved A and B block elements, and showing high homology to the human Alu‐Sx subfamily consensus sequence. Upstream of the Alu repeat were noted a TATA box, a CAAT motif and two activating transcription factor (ATF)‐like binding sites, which represent putative regulatory elements directing Alu transcription. In addition, the 25 and 35 N‐terminal amino acid residues of COPA and its bovine homologue were identical to xenin‐25 and proxenin, respectively. Xenin‐25 is a gastrointestinal hormone that stimulates exocrine pancreatic secretion. This peptide is related to xenopsin, neurotensin and neuromedin N which are bioactive peptides derived from larger precursors via proteolytic cleavage by cathepsin E at processing sites determined by conserved C‐terminal sequences, i.e. proline/valine‐X‐X‐hydrophobic amino acid. Given the conformity of the C‐terminal residues of xenin‐25 (PWIL) and of its progenitor molecule, proxenin (VIQL), it is proposed that these peptides are generated by a similar mechanism of post‐translational modification involving a parent precursor represented by the α‐subunit of coatomer.