Fig. 5. Oviduct-secreted glycoprotein (OGP) is not the peripherally associated, ZP3-independent ligand. Inhibition of wild-type and GalT I-null sperm binding to eggs by ovulated zona glycoproteins (three ZP/µl) prepared from wild-type and OGP-null females (Araki et al., 2003). Each bar represents the mean±s.d.; n=1 experiment, which was carried out in triplicate. Wild-type and GalT I-null sperm are equally inhibited from binding to ovulated eggs by zona glycoproteins isolated from wild-type and OGP-null females. The broken line indicates the number of sperm bound in the control (buffer).