The prosomal protein of 27 kDa and a nuclear 38 kDa protein are immunologically related

A monoclonal antibody, recognizing the prosomal 27 kDa protein, was used to detect prosomal proteins in nuclear fractions. Protein gel electrophoresis and immunoblotting revealed large amounts of a 38 kDa protein and in very low amount a 27 kDa protein reacting with the monoclonal antibody. Immunoblot analysis of V8 proteolytic fragments demonstrated that both proteins are intimately related and suggest that the nuclear 38 kDa protein could be a precursor of the 27 kDa protein (pros P 27) which is a structural component of cytoplasmic prosomes.