Plasma Membrane Glycoproteins of Ciona intestinalis Spermatozoa that Interact with the Egg1

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Abstract
In the ascidian Ciona intestinalis the species‐specific interaction between the spermatozoon and the egg occurs between the vitelline coat (VC) of the egg and the plasma membrane of the apical part of the head of the spermatozoa. Concanavalin A (Con A)‐binding sites are present on this area of the sperm surface. We used Con A to identify and isolate the spermatozoon plasma membrane components that may be involved in the interaction with the VC. These glycoproteins have been identified on SDS‐PAGE of a sperm membrane fraction (SMF) enriched with the extermal proteins, after incubation of the gel with 3H‐Con A. Affinity chromatography on Con A‐agarose has been used for the purification of sperm plasma membrane proteins with and affinity for the lectin. The biological activity of the Con A‐retained fraction was determined with binding and fertilization assays.