PROSITE documentation PDOC52060

Egg vitelline envelope receptor for lysin (VERL) repeat profile

Fertilization is a complex process involving a cascade of molecular interactions, including gamete release, sperm chemoattraction to the egg, passage of the sperm through the egg jelly, attachment to the vitelline envelope, induction of the sperm acrosome reaction, dissolution of the vitelline envelope (VE), and fusion of the sperm-egg plasma membranes. Each of these stages is mediated by specific recognition systems, often facilitated by gamete recognition proteins (GRPs). GRPs are crucial to many of these stages and have been identified in various taxa, including mammals, marine invertebrates, insects, plants, and protists. One of the best characterized comes from the vetigastropods, including Haliotis (abalone) and Tegula, snail genera, where sperm lysin creates a hole in the VE, allowing sperm to cross this fertilization barrier by a nonenzymatic process involving binding to a large VE glycoprotein, the vitelline envelope receptor for lysin (VERL). Binding of lysin to VERL causes the VERL molecules to lose cohesion and splay apart creating the hole. VERL contains a tandemly repeated array of an ~120 amino acid motif that is believed to be the lysin-binding sequence. Most of the 22 abalone VERL repeats evolve via concerted evolution, such that repeats within a species are more similar to each other than to any in different species. However, the first two VERL repeats do not undergo concerted evolution and instead diverge via positive selection. In addition to its repeat array, VERL also contains a motif of approximately 260 amino acids known as the zona pellucida (ZP) domain (see <PDOC00577>). The ZP domain is found in diverse eukaryotic structures including the egg coats of vertebrates, where it is believed to play an important structural role in the formation of intermolecular fibers [1,2,3,4,5,6].

The VERL repeat adopts a immunoglobulin-like β sandwich core fold (see <PDB:5II4>). It contains 4 Cys forming 2 disulfide bridges with 1-4, 2-3 connectivity [6].

The profile we developed covers the entire VERL repeat.