Ultrastructural localization of a peroxisomal protein in rat liver using the specific antibody against the non-specific lipid transfer protein (sterol carrier protein 2).

An antibody against the non-specific lipid transfer protein from rat liver was purified by immunoabsorbent affinity chromatography. This antibody in conjunction with protein A-colloidal gold was used to localize the transfer protein in rat liver by electron microscopy. Labeling by this immunocytochemical technique was found to be mainly restricted to the peroxisomes; low labeling was observed in the cytoplasm. Subsequent analysis of isolated peroxisomes by immunoblotting indicated that the non-specific lipid transfer protein (mol. wt. 14800) was absent from this organelle and that a protein of molecular weight 58000 was responsible for the immunological response. Immunoblotting of the membrane-free cytosol showed the presence of both proteins. It remains to be established to what extent the non-specific lipid transfer protein in the cytosol and the high-molecular weight protein in the peroxisomes are related.