Abstract

Using the yeast two-hybrid system, we studied the physical interaction between the complete C 1 and C 2 cytosolic domains of Xenopus laevis type 9 (xl9C 1, xl9C 2) and the C 2 domain of rat type 6 (r6C 2) adenylyl cyclase (AC). Heterodimerization between xl9C 1 and xl9C 2 and homodimerization between C 2 (but not C 1) domains was observed. Interaction between C 2 and human G?s (hG?s) was also detected and was dependent on G?s activation. In contrast X. laevis G?s (xlG?s), which is 92% identical to hG?s, was unable to interact with any of the three AC cytosolic domains tested, corroborating previous findings that showed no effector activation. Through the construction of chimeras, we demonstrated that the amino-terminal half of xlG?s was responsible for the lack of interaction with AC. Chimeras between mouse G?i2 and G?s (N-mG?i2/C-G?s), that have previously shown to activate AC to a higher extent than wild-type G?s, also interacted with the C 2 cytosolic domain and with a higher affinity. Interestingly, N-mG?i2/C-xlG?s chimera was not only able to interact with C 2 but also with the C 1 cytosolic domain. Copyright (C) 1998 Federation of European Biochemical Societies.