1a. Amino acid sequence of the longest known (474-amino acid) human SERBP1 isoform. The single-letter amino acid code is used. Regions that are encoded by alternatively-spliced exons and therefore not present in some of the shorter isoforms are shown in gold (i.e., the 63-amino-acid N-terminal region), red, blue or green (see Fig. 1b for more details). The two regions that are targets for arginine methylation by PRMT1 (typically, repeats of sequence RGG or RGR) are shown in grey. The C-terminal region required for interaction with RACK1 is underlined.
1b. Human SERBP1 variants. BLAST searches of amino acid sequence data in GenBank using the 474-amino acid SERBP1 isoform as a query yielded 9 additional isoforms, all encoded by SERBP1 and generated by alternative mRNA splicing. Each of these isoforms differs from the 474-amino acid isoform in that it lacks specific blocks of sequence, as shown.