Abstract
SRPK1 is an evolutionary conserved protein kinase that specifically phosphorylates its substrates at serine residues located within arginine-serine-rich (RS) domains. We have previously reported the existence of a second less abundant isoform in humans, SRPK1a, which is formed from alternative splicing of the SRPK1 gene and contains an insertion of 171 amino acids at its N-terminal domain (Nikolakaki et al., 2001). In the NCBI database SRPK1a is annotated as a related to SRPK1-mRNA sequence coding for protein CAC39299.1. Here, we present data on the conservation of the extra sequence of SRPK1a in mammals. Furthermore, the retrieved sequences were comparatively analyzed and data on their evolutionary origin and relationships are also presented.