Open AccessIsopycnic Centrifugation of Free and Membrane‐Bound Polysomes from Rat Liver
Author(s) -
Dissous Claude,
Caner François,
Krembel Jean
Publication year - 1974
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1974.tb03469.x
Subject(s) - polysome , centrifugation , membrane , isopycnic , differential centrifugation , ribonuclease , density gradient , biology , sucrose , sucrose gradient , biochemistry , chemistry , biophysics , ribosome , rna , physics , quantum mechanics , gene
Rat‐liver polysomes have been studied in CsCl buoyant density gradients.1 Membrane‐bound polysomes band at a density of about 1.53 g/cm 3 , whereas free polysomes are recovered from the gradients at two higher densities (about 1.56 and 1.545 g/cm 3 , called, respectively, type I and II). Both types of free polysomes appear heterogeneous on sedimentation. They are found in all regions of the polysomal gradient. 2 Monoribosomes obtained after mild ribonuclease digestion of either free or membrane‐bound polysomes band at a unique density (1.55 g/cm 3 ). 3 The two types of free polysomes have quite different sedimentation behaviors in the preparative discontinuous sucrose gradient. After 6 h of centrifugation at 113000 × g av the polysomal pellet is mainly composed of the type I. Type II remains with rough membranes at the lower interphase and is recovered in the pellet only after a 20‐h centrifugation. 4 During starvation, it appears that the proportion of type I polysomes increases, while the proportion of type II decreases.Possible interaction with membranes of the type II polysomes is discussed.