Studies of the uptake of macromolecules by cells. II. Metabolic aspects of protein uptake by cells of the Ehrlich–Lettré ascites carcinoma

Abstract

The close interrelationship between cellular metabolism and the process involved in the uptake of protein by cells was studied. The activation energy in this process suggests that the rate-determining step for the overall process is driven by an enzymatic reaction. The driving force was found to be derived from various pathways in glucose metabolism. The uptake of protein under aerobic conditions is higher than that under anaerobic conditions. Inhibitors which were studied, such as iodoacetate, sodium fluoride, sodium azide, and oligomycin caused an inhibition in the uptake of protein. It is probable that the energy present in ATP is involved in driving the process of protein uptake and that the control mechanism for the process is bioenergetic in character. The major modification of cellular metabolism coincident with the uptake of protein was found to be in an enhanced nuclear RNA turnover. The significance of a metabolic involvement was further clarified by using actinomycin D and puromycin. Both inhibitors brought about an inhibition in the process of protein uptake.