Abstract
The properties of the ribosomes and the messenger RNA associated with membranes were studied in HeLa cells. There are two classes of membrane-bound ribosomes which can be distinguished by their attachment to the membranes. The loose ribosomes are dissociated from the membranes by treatment with EDTA, puromycin and RNase. The tight ribosomes are refractory to these agents. About 35 to 40% of the membrane-bound messenger RNA is dissociated from the membranes with EDTA. The EDTA-resistant messenger RNA is partially dissociated from the membranes with puromycin. Ribosomes and messenger RNA re-associate with the membranes after reversal of the puromycin treatment.