The interaction of nitric oxide (NO) with the yeast transcription factor Ace1: A model system for NO-protein thiol interactions with implications to metal metabolism

Nitric oxide (NO) was found to inhibit the copper-dependent induction of th e yeast CUP1 gene. This effect is attributable to an inhibition of the copp er-responsive CUP1 transcriptional activator Ace1, A mechanism is proposed whereby the metal binding thiols of Ace1 are chemically modified via NO- an d O-2-dependent chemistry, thereby diminishing the ability of Ace1 to bind and respond to copper. Moreover, it is proposed that demetallated Ace1 is p roteolytically degraded in the cell, resulting in a prolonged inhibition of copper-dependent CUP1 induction. These findings indicate that NO may serve as a disrupter of yeast copper metabolism. More importantly, considering t he similarity of Ace1 to other mammalian metal-binding proteins, this work lends support to the hypothesis that NO may regulate/disrupt metal homeosta sis under both normal physiological and pathophysiological circumstances.