    2.7.1.185 | hanging drop method, crystal structure of mevalonate-3-kinase in the apo form, and with bound substrates is determined and compared to mevalonate diphosphate decarboxylase structures. The crystal structure of mevalonate-3-kinase provides insight into the mechanism of mevalonate diphosphate decarboxylase. Despite sharing nearly identical overall folds, important active site differences are identified. Glu140 in the center of the mevalonate-3-kinase active site is responsible for binding mevalonate while excluding mevalonate 5-diphosphate, Arg185/Ser105 catalyze phosphate transfer, and an invariant Asp/Lys pair previously thought to be responsible for phosphorylation in mevalonate diphosphate decarboxylase, is missing in mevalonate-3-kinase and replaced by non-essential Thr275/Leu18. A model is proposed in which mevalonate-3-kinase and mevalonate diphosphate decarboxylase both phosphorylate by stabilizing a phosphotransfer transition state (mevalonate-3-kinase via Arg185/Ser105, mevalonate diphosphate decarboxylase via Lys188), suggesting the invariant Asp/Lys pair unique to mevalonate diphosphate decarboxylase may be critical for the decarboxylation step rather than phosphorylation |
