Cloning and expression of a human pro(tea)some β‐subunit cDNA: A homologue of the yeast PRE4‐subunit essential for peptidylglutamyl‐peptide hydrolase activity

Abstract
The cDNA encoding a human prosome β‐subunit (HSBpros26) was isolated from a lymphoma library using the cDNA of theXenopus homologue as a probe. The cDNA contains an open reading frame encoding a protein of 233 amino acids and a calculated molecular weight of 25,909. Comparison with interspecies homologues of HSBpros26 fromXenopus (XLB), rat (RN3) and yeast (PRE4) reveals a high degree of identity between the β‐subunits except for the N‐terminal end, which is probably cleaved post‐translationally. The complete coding sequence of HSBpros26 has been expressed inE. coli. The produced protein of about 27 kDa reacts with the prosomal monoclonal antibody MCP205, kindly provided by Dr. K. Hendil. The molecular weight of the native protein is about 28 kDa indicating that the protein is present as monomers. Finally partially purified HSBpros26 preparations do not contain any proteolytical activity.