Sushi Repeat Containing Protein, X-Linked (SRPX)

SRPX spans 80 kb and contains 12 exons, at least 2 of which are alternatively spliced and have predicted products of 464 and 471 amino acids, respectively. Conceptual translation of the open reading frames showed 1 product with a 30-amino acid signal peptide, which is absent from the alternative transcript, followed by 3 complement control protein domains, a hydrophobic region with a possible role in membrane anchorage, and a short 17-amino acid putative cytoplasmic C terminus. An alternative first exon contains a 39-amino acid open reading frame that is rich in serine and threonine residues and contains a potential chondroitin/dermatin sulfate attachment site. Northern analysis showed ETX1 expression within the retina and heart, with lower levels in several other tissues.