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Transforming glycoprotein coded by the fms oncogene from the Susan McDonough strain of feline sarcoma virus (SM-FeSV). The oncogene protein v-fms lacks sequences, which, in the highly homologous proto-oncogene protein c-fms (CSF-1 receptor), normally serve to regulate its tyrosine kinase activity. The missing sequences in v-fms mimic the effect of ligand and lead to constitutive cell growth. The protein gp120 (v-fms) is post-translationally modified to generate gp140 (v-fms).