Abstract

Using the yeast two-hybrid system, me 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 Cg and human Gets (hG alpha s) was also detected and was dependent on Gas activation. In contrast X. laevis G alpha s (xlG alpha s), which is 92% identical to hGas, 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 aminoterminal half of xIG alpha s was responsible for the lack of interaction with AC. Chimeras between mouse G alpha i2 and G alpha s (N-mG alpha i2/C-G alpha s), that have previously shown to activate AC to a higher extent than wild-type Gas, also interacted with the C-2 cytosolic domain and with a higher affinity. Interestingly, N-mG alpha i2/C-xlG alpha s chimera was not only able to interact with C-2 but also with the C-1 cytosolic domain. (C) 1998 Federation of European Biochemical Societies.