Abalone lysin: the dissolving and evolving sperm protein

Abalone sperm lysin is a non-enzymatic protein that creates a hole for sper m passage in the envelope surrounding the egg. Lysin exhibits species-speci ficity in making the hole and it evolves rapidly by positive selection. Our studies have focused on combining structural, biochemical, and evolutionar y data to understand the mechanism of action and evolution of this remarkab le protein. Currently, more is known about lysin than about any other prote in involved in animal fertilization. We present an hypothesis to explain ly sin's rapid evolution and the evolution of species-specific fertilization i n this order of mollusks, We also propose a two-step model for lysin's acti on in which a dimer of lysin binds species-specifically to its glycoprotein receptor, and then monomerizes and binds the receptor in a non-species-spe cific manner. This experimental system yields data relevant to the general problem of molecular recognition between cell surfaces, and is also importa nt to our thinking about how new species arise in the sea, (C) 2001 John Wi ley & Sons, Inc.