Molecular modeling of the hamster adrenal P450C17

The cytochrome P450C17 (C17) is the steroidogenic enzyme responsible for th e conversion of pregnenolone and progesterone to dehydroepiandrosterone (DH EA) and Delta (4)-androstenedione (AD) respectively. This conversion is ach ieved by two enzymatic activities, 17 alpha -hydroxylase and 17,20-lyase, l ocated at the same active site. In man, the adrenal C17 basically only prod uces DHEA. We have shown that the hamster adrenal C17 produces DHEA as well as AD. Moreover, the hamster like man produces cortisol as its major gluco corticoid. We can thus compare the hamster and human adrenal C17, and use t heir differences in order to elaborate a strategy for structure-function st udies. We have thus engineered hamster adrenal C17 mutants which possess mo dified enzymatic activities. We also proceeded to elaborate a three-dimensi onal model of the hamster C17 to visualise the structural impact of these m utations. This model demonstrates that the mutations created are not locali sed at the active site, but rather in surrounding regions. These could affe ct the conformation of the active site, in turn, modulating the 17 alpha -h ydroxylase and 17,20-lyase activities. For example, the mutation T202N is l ocated next to Val 482 and Val 483 which compose the roof of the active sit e. This mutation decreased both 17 alpha -hydroxylase and 17,20-lyase activ ities, indicating the importance of the roof of the active site for general functionality of the C17.