The phosphorylation of proteins from murine splenic lymphocytes was studied. When the phosphorylation of proteins in extracts from Concanavalin A (ConA)-treated lymphocytes was compared with that of resting lymphocytes, there was only one detectable difference between them. A protein of 135 000 mol. wt was highly phosphorylatable in extracts from ConA-treated cells while phosphate incorporation into this protein was slight in extracts from untreated cells. This effect could be observed 12 h after ConA treatment and was maximal during S phase. This soluble protein was also phosphorylated in intact lymphocytes.
Bibliographical noteFunding Information:
We thank Carolyn E. McSwigan and Cathy Marquardt for their excellent technicala ssistance.T his work was supportedb y a National Foundation-Basil O’Connor Grant, USPHS grants GM 22492a nd CA 16228a, nd a National Leukemia Association grant.