Identification of two additional v-sea-encoded proteins in avian erythroblastosis virus, S13-infected fibroblasts.

Rabbit antibodies prepared against a v-sea-encoded polypeptide expressed in bacteria were used to characterize the v-sea-encoded proteins in cells transformed by the avian erythroblastosis virus, S13. In addition to the two previously described v-sea-encoded proteins, gp155 and gp70, two additional proteins were identified of molecular weights 38,000 and 36,000 Da. Interestingly, these two proteins were found only in fibroblasts infected with the S13 virus and not in S13-transformed erythroid cells. These two proteins were phosphoproteins, but, unlike the two previously characterized v-sea-encoded proteins, they did not appear to be modified by the addition of N-linked sugars. Possible mechanisms for the biosynthesis of these two new proteins are discussed.