Structurally these proteins consist of a closed bundle of helices with a right-hand twist.
Lysin and SP18, both characterised in abalone, are two evolutionarily related fertilization proteins that have distinctive roles.
[1] Lysins exhibit species-specific binding to their egg receptor, possibly through differences in charged surface residues.
Despite a similarity in the overall fold, the variation in the surface features of SP18 and lysin account for their different roles in fertilization.
[3] The molecular basis of VERL-lysin interaction was revealed in June 2017 by researchers at Karolinska Institutet and ESRF, who reported X-ray crystallographic and biochemical studies of both species-specific and non-species-specific complexes between the two proteins.