STRUCTURAL AND MECHANISTIC ASPECTS OF 3C PROTEASES FROM THE PICORNAVIRUS FAMILY

Picornavirus 3C proteases are prime targets for rational drug design. This viral protease appears in a large number of viruses from the Pico rnavirus family that cause serious disease syndromes, and it has an im portant role in the life cycle of the virus, processing the translatio n product of the Picornavirus genome by progressive co- and posttransl ational cleavages. It is, therefore, important to gain structural and mechanistic information about this family of enzymes. We concentrate i n this paper on the specific features of the 3C; particularly, we are trying to show that the 3C constitute a new family to enzymes which is neither a serine- nor a cysteine-type protease. General basic theory on the behavior of sulfur nucleophile vs the behavior of oxygen nucleo phile regarding the nucleophilic attack on carbonyl compounds and the possible determinants in the structure of 3C viral proteases of rhinov irus IA are being discussed.