Open AccessTwo subcellular locations for peripheral‐type benzodiazepine acceptors in rat liver
Author(s) -
O'BEIRNE Gerard B.,
WOODS Margaret J.,
WILLIAMS D. Clive
Publication year - 1990
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1990.tb15380.x
Subject(s) - differential centrifugation , mitochondrion , golgi apparatus , isopycnic , cell fractionation , chemistry , acceptor , microsome , biochemistry , subcellular localization , endoplasmic reticulum , centrifugation , enzyme , biophysics , biology , cytoplasm , physics , condensed matter physics
Subcellular fractionation of rat liver by differential centrifugation showed the mitochondrial fractions to have the greatest enrichment of ‘peripheral‐type’ benzodiazepine acceptor. Two peaks of acceptor sites were found on isopycnic density‐gradient centrifugation, one peak (ϱ= 1.19 g/ml) corresponding to the peak of mitochondria as judged by marker enzyme distribution and by transmission electron microscopy, and the other peak (ϱ= 1.17 g/ml) which is not mitochondrial as judged by the lack of mitochondrial enzyme markers. Whereas the density of the mitochondrial acceptor was sensitive to sonication and was shown to have an outer‐membrane location, the density of the non‐mitochondrial acceptor was insensitive to sonication. The non‐mitochondrial acceptor was shown not to be associated with Golgi, lysosomes, rough endoplasmic reticular microsomes, peroxisomes, or some type of plasma membranes, as jugged by differences in the distribution of marker activities. No enrichment of benzodiazepine acceptor was found in the purified nuclear fraction. Both acceptors were shown to be peripheral‐type high‐affinity acceptors as judged by ligand specificities and by photoaffinity labelling.