Transfer RNA Associated with Rat Liver Plasma Membranes

Abstract

Plasma membranes were isolated by differential and gradient centrifugation of rat liver homogenates. The isolation was monitored by assay of the plasma membrane marker enzymes 5’-nucleotidase, Mg2+ activated ATPase and alkaline p-nitrophenyl phosphatase. Gross contamination was estimated by electron microscopy and assay of the endoplasmic reticulum marker enzyme glucose-6-phosphatase. RNA was extracted from purified plasma membranes and aminoacylated with radioactive amino acids. The amino acid acceptor activity of this RNA could not be attributed to contamination with transfer RNA from other cell fractions or adherence of cytoplasmic low molecular weight RNA during the isolation. This is the first demonstration that transfer RNA is associated with purified plasma membrane.