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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

Published online by Cambridge University Press:  01 July 1997

V. T. K. CHOW
Affiliation:
Human Genome Laboratory, Department of Microbiology, Faculty of Medicine, National University of Singapore, Kent Ridge, Singapore 119260
H. H. QUEK
Affiliation:
Human Genome Laboratory, Department of Microbiology, Faculty of Medicine, National University of Singapore, Kent Ridge, Singapore 119260
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Abstract

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.

Type
SHORT COMMUNICATION
Copyright
© University College London 1997

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