CLONING AND EXPRESSION OF A HUMAN PRO(TEA)SOME BETA-SUBUNIT CDNA - A HOMOLOG OF THE YEAST PRE4-SUBUNIT ESSENTIAL FOR PEPTIDYLGLUTAMYL-PEPTIDE HYDROLASE ACTIVITY

The cDNA encoding a human prosome beta-subunit (HSBpros26) was isolate d from a lymphoma library using the cDNA of the Xenopus 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. Compariso n with interspecies homologues of HSBpros26 from Xenopus (XLB), rat (R N3) and yeast (PRE4) reveals a high degree of identity between the bet a-subunits except for the N-terminal end, which is probably cleaved po st-translationally. The complete coding sequence of HSBpros26 has been expressed in E. coli. The produced protein of about 27 kDa reacts wit h the prosomal monoclonal antibody MCP205, kindly provided by Dr. K. H endil. The molecular weight of the native protein is about 28 kDa indi cating that the protein is present as monomers. Finally partially puri fied HSBpros26 preparations do not contain any proteolytical activity.