Dynamics of Carbohydrate Affinities at the Cell Surface: DISCUSSION(3)
Sperm-oviduct interactions cannot be investigated in situ at the biochemical level. However, several in vitro studies have shown that mammalian sperm binding to the oviduct is mediated by carbohydrate interactions. For bovine species, the animal model of the current investigation, this interaction appears to be fucose specific. We have set up a biochemical assay to quantify the binding affinity of the apical surface of the sperm head, and for this purpose, we first isolated this specific plasma membrane area (SPM) and constructed biotinylated carbohydrate conjugates to quantify SPM carbohydrate-binding capacity and the potency of unconjugated carbohydrates to compete in this binding.
Specifically, binding of fucose-PAA-biotin and LeA-PAA-biotin to immobilized SPM was investigated. The fact that immobilized SPM had high binding capacity for both biotinylated probes and that this binding was confined to the apical tip area of the sperm head confirms that sperm bind fucosylated molecules at their surface area involved in sperm-oviduct binding. However, the observation that fucose-PAA-biotin showed higher binding specificity for isolated SPM than LeA-PAA-biotin is in contrast with previously published data.