A non-virion surface antigen on Moloney sarcoma virus-transformed non-producer and producer cells

Sera from STU mice bearing sarcomas induced by cells producing the Moloney sarcoma-helper-virus (M-MSV/MLV) complex were cytotoxic for these cells as well as for M-MSV non-producer and M-MLV producer cells. Analysis by polyacrylamide gel electrophoresis of 125I-labelled surface antigens immunoprecipitated with such sera revealed the virus envelope glycoprotein gp71 on the producer cells and an additional antigen of mol. wt 55 K on the M-MSV-transformed producer and non-producer cells. This antigen was not found on non-transformed M-MLV-producing cells and was neither related serologically to structural polypeptides of murine C-type viruses nor to components of embryonal STU mouse fibroblasts and foetal bovine serum.