A fraction that stimulates hamster sperm motility can be obtained from human serum by Sephadex gel filtration (Morton & Bavister, 1974). The protein-rich fractions potentiate this activity and effectively induce the acrosome reaction. Here, we describe attempts to determine the type of protein that may be involved.
The methods used to prepare the motility-stimulating fraction from human serum and for assessing its activity were as previously described (Morton & Bavister, 1974). To help identify which serum component induced the acrosome reaction, serum proteins were chromatographically separated on Sephadex G-150 (5 ml pooled human serum fractionated on 130 ml bed volume G-150 in a 1·5×90 cm column, fraction size 1·6 ml, flow rate 10 ml/hr). Protein was monitored by absorption at 280 nm with an LKB Uvicord II (see Text-fig.