Reexamination of the sequence of the sea urchin egg receptor for sperm: Implications with respect to its properties

A reexamination of the cDNA clones of the Strongylocentrotus purpuratus sea urchin egg receptor for sperm resulted in several important changes to the sequence. By using both rapid amplification of cDNA ends (RACE) and Northern blot analysis for confirmation, the corrected deduced amino acid sequence was shown to lack a classical signal peptide. In addition, a frame shift resulted in a stop codon terminating the deduced sequence prior to a putative transmembrane domain, thereby truncating the protein to 889 amino acids. The deduced amino acid sequence of the receptor has high sequence similarity to the hsp 110 subfamily of proteins. These findings on the primary structure of the egg receptor for sperm raise important questions concerning the mechanism by which the heavily glycosylated receptor is localized to the extracellular surface of the egg and to the cortical granules. (C) 1997 Academic Press.