Mammalian adenylate cyclases are predicted to possess complex topologies, comprising two cassettes of six trans-membrane-spanningmotifs followedbyacytosolic, catalytic ATP-binding domain. Recent studies have begun to provide insights on the tertiary assembly of these proteins; crystal-lographic analysis has revealed that the two cytosolic domains dimerize to forma catalytic core, whilemore recent biochemical and cell biological analysis shows that the two transmembrane cassettes also associate to facilitate the functional assembly and tra ckingof the enzyme. .
