The short isoform of Sorcin (soluble resistance-related calcium-binding protein) (a 19,000-dalton peptide) was isolated for the first time by Meyers and coworkers in vincristine-resistant Chinese hamster cells (DC-3FVCRd-5). A similar protein (Mr = 19,000; pI = 5.7) was also found in a vincristine-resistant mouse line (Meyers and Biedler 1981). The gene of Sorcin (SRI) codifying for the longest isoform was identified around the multidrug resistance gene region of human chromosome 7q21.1.
The gene can generate at least four alternative transcripts, i.e., isoforms A (a primary transcript of 15 kb divided in eight exons and seven introns, transcribed in a 198-amino-acid-long protein), B, C, and D, yielding shorter forms of the protein, lacking part of the N-terminal domain and/or of the final residues of the C-terminal domain. The isoform A was identified by...
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