Differential effects of mutating the B-C loop and/or Tyr⁴²¹ of the F-G loop in receptor activation.

(A) Scatchard plot transformation of binding isotherms for ¹²⁵I-GM-CSF and ¹²⁵I-IL-3 to cells transfected with wild-type β_c (○) or³⁶⁵AAAA³⁶⁸ mutant β_c (•). (B) Western blot of wild-type and mutant β_c after stimulation with various concentrations of IL-3. The blot was probed for phosphotyrosine (upper panel) and β_c (lower panel). The double bands in each lane of the gels represent glycosylation variants of β_c.23