Role of arginine-304 in the diphosphate-triggered active site closure mechanism of trichodiene synthase

The X-ray crystal structures of R304K trichodiene synthase and its complexes with inorganic pyrophosphate (PP(sub i)) and aza analogues of the bisabolyl carbocation intermediate are reported. Structural analysis of the R340K mutant and comparison with the monoterpene cyclase (+)-bornyl diphosphate synthase suggest that the significant loss in activity results from compromised activation of the PP(sub i) leaving group.