Full-length sequence of VERL, the egg vitelline envelope receptor for abalone sperm lysin.

Abalone sperm use 16 kDa lysin to create a hole in the egg vitelline envelope (VE) by a species-specific, nonenzymatic mechanism. To create the hole, lysin binds tightly to VERL (the VE receptor for lysin), a giant, unbranched glycoprotein comprising 30% of the VE. Binding of lysin to VERL causes the VERL molecules to lose cohesion and splay apart creating the hole. Lysin and VERL represent a cognate pair of gamete recognition proteins, one male the other female, which mediate fertilization. The coevolution of such cognate pairs may underlie the establishment of species-specific fertilization which could be a component of the mechanism to achieve reproductive isolation and hence new species. Here we present the full-length cDNA sequence (11,166 bp) of VERL from the red abalone (Haliotis rufescens). There are 42 amino acids from the start Met residue to the beginning of the first 'VERL repeat'. Most of VERL (9981 bp; 89.4%) consists of 22 tandem repeats of a approximately 153 amino acid sequence that is predicted to be beta-sheet. The last VERL repeat is followed by 353 non-repeat amino acid residues containing a furin cleavage site (RTRR), a ZP domain and a hydrophobic COOH-terminus with a 3' UTR of only 10 nucleotides. VERL repeats 3-22 have been subjected to concerted evolution and consequently have almost identical sequences. Curiously, comparisons of repeats from other species shows that repeats 1 and 2 of red abalone VERL have not been subjected to concerted evolution since the divergence of the red species from the other six California species.