PRESENCE OF CHROMATIUM-VINOSUM CHAPERONIN-10 AND CHAPERONIN-60 IN MITOCHONDRIA AND PEROXISOMES OF RAT HEPATOCYTES

In the present study we report the occurrence of chaperonins, cpn10 an d cpn60, in Chromatium vinosum and rat hepatocytes, using specific pol yclonal antibodies in conjunction with the protein A-gold immunocytoch emical technique. As demonstrated hy quantitative evaluations, the imm unolabeling for cpn10 and cpn60 in C vinosum cells was associated prim arily with the bacterial cell envelope. In rat liver homogenates, West ern immunoblotting analysis has shown that antibodies to cpn10 from C vinosum recognize an unique 25-kDa protein that remains to be further characterized. On the other hand, the antibody to cpn60 from C vinosum revealed the presence of a 60-kDa protein in the rat liver homogenate s. Immunofluorescence on rat liver tissue revealed an intracellular gr anular labeling for both chaperonins. On the other hand, using the pos t-embedding immunoelectron microscopy technique cpn10 and cpn60 were l ocalized specifically in liver mitochondria and peroxisomes. Interesti ngly, further analysis of the labeling distribution confirmed the asso ciation of both proteins with the mitochondrial inner membrane whereas in the peroxisomes the chaperonins appeared to be located in the matr ix, away from the limiting peroxisomal membrane. The colocalization of both chaperonins suggests that, as in other bacteria as well as eukar yotic cells, they may act in tandem for the proper folding of particul ar proteins.