Partial Proteolytic Digestion of the Mammary Prolactin Receptor: Identification of Smaller Prolactin Binding Fragments

Abstract

Partial proteolytic digestion of the mammary prolactin (PRL) receptor was used to generate receptor fragments and analyze their immunoreactivity and PRL binding properties. Tryptic digestion of the PRL receptor produced two immunoreactive fragments (Mr ≈ 30,000 and ≈ 15,000) that reacted with a monoclonal anti-PRL receptor antibody and still specifically bound PRL, while the complete immunoreactive PRL binding unit (Mr ≈ 42,000) disappeared. Neither chymotrypsin nor V8 protease were able to generate any immunoreactive receptor fragments. These receptor fragments may represent smaller PRL binding receptor form(s) of biological significance.