Plasma membrane proteins and glycoproteins from chinese hamster cells sensitive and resistant to actinomycin D

Plasma membrane proteins and glycoproteins have been isolated from Chinese hamster cells of the spontaneously transformed DC-3F parental cell line and the DC-3F/AD X line with a high level of acquired resistance to actinomycin D. Plasma membrane preparations from both cell lines band at 1.16 g/ml after isopycnic centrifugation. We present evidence to indicate differences in the leucylpeptide backbones of the antibiotic-sensitive cells and the drug-resistant DC-3F/AD X cells. In addition, there are differences in the plasma membrane glycopeptides of the two cell lines as revealed by sodium dodecyl gel electrophoresis. Drug-resistant cells synthesize a surface glycopeptide which is much larger than the major one present on the drug-sensitive cells. Both of these cell lines are devoid of 5′-nucleotidase and alkaline phosphatase activities. The role of plasma membrane protein differences in drug-resistant cells is discussed.