Fig. 4. Binding of sperm plasma membrane and blood cell GSTs to ¹²⁵I-SZP and of labelled sperm GST-Pi and Mu to SZP. Proteins were blotted onto nitrocellulose membranes and were probed with labelled SZP. (A) Dot blots of (a1) total sperm plasma membrane GSTs probed with ¹²⁵I-SZP, (a2) total sperm plasma membrane GSTs preadsorbed with cold SZP and subsequently probed with ¹²⁵I-SZP, (b1) total blood cell GSTs probed with ¹²⁵I-SZP, (b2) total blood cell GSTs preadsorbed with cold SZP and probed with ¹²⁵I-SZP, (c1) BSA (5 µg) probed with ¹²⁵I-SZP and (c2) BSA (5 µg) preadsorbed with cold SZP and subsequently probed with ¹²⁵I-SZP. (B) Volume quantitation of `A' using a Molecular Dynamics Phosphorimager with Imagequant software package. Groups are as described in A. (C) Binding of radioiodinated GST Pi and GST Mu purified from sperm plasma membranes to SZP coated on to microtitre plates (1 µg/well). Binding of (a) labelled sperm plasma membrane GSTs; (b) labelled sperm plasma membrane GSTs preadsorbed with SZP (10 µg/ml); (c) labelled sperm plasma membrane GST-Mu; (d) labelled sperm plasma membrane GST Mu preadsorbed with SZP (10 µg/ml); (e) labelled sperm plasma membrane GST-Pi; and (f) labelled GST Pi preadsorbed with SZP (10 µg/ml).