Oocyte adenylyl cyclase contains Ni, yet the guanine nucleotide‐dependent inhibition by progesterone is not sensitive to pertussis toxin

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Abstract
The possible susceptibility to pertussis toxin of the guanine nucleotide‐dependent inhibition of oocyte adenylyl cyclase by progesterone was investigated. This action of progesterone is mediated by a membrane bound receptor as opposed to a receptor of cytosolic or nuclear localization. However, the inhibitory effect of progesterone was unaffected by pertussis toxin, even though the oocyte membrane Ni was fully ADP‐ribosylated with pertussis toxin, as revealed by lack of further [32P]ADP‐ribosylation on subsequent re‐incubation with pertussis toxin. These results indicate that the action of progesterone, in spite of being nucleotide‐dependent, is either not mediated by Ni, suggesting the existence of an additional nucleotide regulatory component, or if mediated by Ni, involves a mode of regulation of this coupling protein that is different from that by which all other inhibitory hormones act on adenylyl cyclase.