Figure 6. In vitro sulfonation of (A) caput and (B) cauda epididymal sperm membrane cholesterol by bovine recombinant estrogen sulfotransferase (EST). High-performance thin-layer chromatography analysis of lipid extracts of caput and cauda spermatozoa from 2 different bulls incubated in the presence (+) or absence (–) of recombinant EST and its cofactor phosphoadenosine phosphosulfate. (Left Panels) Stained lipids. (Right Panels) Sulfated sterols revealed by autoradiography. Migration of lipid markers is indicated on the left of the panels. CH indicates cholesterol; CH-S, cholesteryl sulfate; PC, phosphatidyl choline; PE, phosphatidyl ethanolamine; PI, phosphatidyl inositol; SM, sphingomyelin.