Integral membrane polypeptides of XXXX liver peroxisomes: topology and response to different metabolic states.

@entity1375 @entity844 @entity12880 @entity1955 @entity25982 @entity8595 @entity35
@entity35 were treated with @entity12880 , a hypolipidemic drug, and with @entity1955 . Both drugs which are known to cause peroxisome proliferation, and a concomitant increase in peroxisomal @entity844 beta-oxidation activity in liver increased one of the major integral peroxisomal membrane polypeptides (PMPs), with apparent molecular mass of 69-kDa, six- and twofold, respectively. On the other @entity1375 caused a decrease in peroxisomal @entity844 beta-oxidation activity and considerably lowered the concentration of @entity25982 69 in the peroxisomal membrane. Two other PMPs with apparent molecular masses of 36 and 22 kDa were not influenced by these treatments. The PMPs with apparent molecular masses of 42, 28, and 26 kDa were shown to be derived from the 69-kDa polypeptide by the activity of a yet uncharacterized endogenous protease during isolation of peroxisomes. Limited proteolysis of intact peroxisomes using proteinase K and subtilisin further substantiated that some portion of the 69-kDa polypeptide extends into the cytoplasm. The 36- and the 22-kDa polypeptides were accessible to proteolytic attack to a much lower extent and, therefore, are supposed to be rather deeply embedded within the peroxisomal membrane. It is demonstrated that peroxisomal @entity8595 synthetase, an integral PMP extending partially into the cytoplasm, and PMP 69 are not identical polypeptides. Comparison of the peroxisomal membrane with that of mitochondria and microsomes revealed that the 69- and 22-kDa polypeptides as well as the bifunctional protein of the peroxisomal @entity844 beta-oxidation pathway were specifically located only in peroxisomes. Considerable amounts of a polypeptide cross-reacting with the antiserum against the 36-kDa polypeptide were found in mitochondria.
