CYTOSOLIC FACTORS MEDIATE PROTEIN INSERTION INTO THE PEROXISOMAL MEMBRANE

Following in vitro translation of the 22 kDa peroxisomal membrane prot ein (Pmp22p), gel filtration analysis of the post-ribosomal supernatan t revealed that Pmp22p forms two complexes, Complex I is of high molec ular weight, results in a crosslinking product of 80 kDa, and by co-im munoprecipitation with anti-TCP1 antibody was identified as TRiC, In c omplex II Pmp22p was crosslinked to a yet unknown polypeptide of 40 kD a (P40), This complex exhibited much higher efficiency to insert Pmp22 p into the peroxisomal membrane compared to complex I, In a model me s uggest that newly synthesized Pmp22p is first bound to TRiC before bei ng transferred to P40 which may function as a cytosolic Pmp22p recepto r. (C) 1997 Federation of European Biochemical Societies.