Presence of tyrosine-O-sulfate in sheep pituitary prolactin

When the metabolically obtained 35S-labelled sheep pituitary prolactin-rich fraction was subjected to chemical deglycosylation the radioactivity was retained in the immunoprecipitable prolactin. 35S-labelled prolactin-rich pituitary extract was fractionated on SDS-PAGE and protein was extracted from prolactin positive bands. When the extracted 35S-labelled prolactin was hydrolysed by alkali and then chromatographed on a thin layer of silica, it showed the presence of a radioactive compound which had an Rf value identical to the standard Tyr-O-SO4 synthesized and characterized in our laboratory.