In Silico study of the conformational flexibility of point mutated Geobacillus stearothermophilus farnesyl diphosphate synthase

Farnesyl diphosphate synthase from Geobacillus stearothermophilus (GsFPPS) is a thermophilic enzyme which belongs to the prenyltransferase family. We found that the point mutation of an amino acid located on the fifth position upstream of the first aspartate-rich motif (FARM) in GsFPPS (tyr81) affects its flexibility and activity. Enzymatic activities of wild-type GsFPPS, Y81D, Y81R, and Y81S were measured by a 14C radioactivity assay. Their flexibilities were assessed by monitoring the fluorescence intensity changes due to the presence of a collisional quencher and also by coarse-grained molecular dynamics (MD) simulations. Y81R and Y81S showed enhanced activities of up to 1.7-fold, while activity of Y81D was reduced by 1.2-fold. The differences in activity between these enzyme variants are caused by the differences in conformational flexibility, especially in terms of the dynamics of the areas near the active site.