A novel mechanism for adenylyl cyclase inhibition from the crystal structure of its complex with catechol estrogen.

Catechol estrogens are steroid metabolites that elicit physiological responses through binding to a variety of cellular targets. We show here that catechol estrogens directly inhibit soluble adenylyl cyclases and the abundant trans-membrane adenylyl cyclases. Catechol estrogen inhibition is non-competitive with respect to the substrate ATP, and we solved the crystal structure of a catechol estrogen bound to a soluble adenylyl cyclase from Spirulina platensis in complex with a substrate analog.

Genetic selection of regulatory mutants of mammalian adenylyl cyclases.

Initial steps in the identification of the Gs alpha-binding site present in mammalian adenylyl cyclases can be achieved with the use of the yeast genetic system described. It must be stressed that this system serves as a means to identify mutants that are candidates; biochemical analysis of these mutants is a next and necessary step in the confirmation of these phenotypes. The system described can be readily adapted for the isolation of additional classes of mammalian adenylyl cyclase mutants including mutants with altered regulation toward forskolin, catalytic abnormalities, or enhanced sensitivities toward activators.