Structural study of a single-point mutant of Sulfolobus solfataricus alcohol dehydrogenase with enhanced activity

Alcohol dehydrogenase from Sulfolobus solfataricus (SsADH) is the only enzyme from Archaea among the structurally studied members of the medium-chain ADH family described so far. Here, we present the three-dimensional structure of the apo form of the mutant N249Y which exhibits increased catalytic activity when compared to the wild-type enzyme. The substitution, located in the coenzyme binding domain, decreases the affinity for NAD(H) cofactor. The rearrangement of segments 248-250 and 270-275, induced by the mutation, suggests an explanation for the lower coenzyme affinity. This study also highlights the role in SsADH catalysis of the flexible loops located at the interface between the catalytic and the coenzyme domains.