[Ultrastructural and biochemical analyses of fragmented microsomal membranes].

Treatment of membranes of rat liver microsomal ghosts in a homogenizer with a Teflon pestle results in fragments strongly differing in their protein--lipid ratios. The fragments obtained can be separated by ultracentrifugation in sucrose density gradient into light and heavy fractions. The light fraction contains predominantly phospholipid vesicles devoid of intramembrane particles on the hydrophobic surfaces of the membrane. The heavy fraction is represented by proteolipid complexes which contain all proteins typical for original ghost membranes and are enriched with neutral lipids. The proteolipid complexes appear as globular particles of the same diameter as the intramembrane particles of microsomal ghosts. It is assumed that the intramembrane particles of microsomes are represented by large polyenzyme proteolipid complexes rather than by individual proteins. The former can be isolated in a pure state.