Screening of agents which convert 'transformed morphology' of Rous sarcoma virus-infected rat kidney cells to 'normal morphology': identification of an active agent as herbimycin and its inhibition of intracellular src kinase.

During the course of screening of agents active in converting the transformed morphology of Rous sarcoma virus-infected rat kidney cells to the normal morphology, we identified an active substance produced by Streptomyces sp. MH237-CF8 as herbimycin. Herbimycin converted almost all cells into the normal morphology. The antibiotic was found to be an inhibitor of p60src-associated protein kinase in the cells.