sentence: The MAP3K9 E319 residue forms hydrogen bonds with R393 and the mutation to lysine will disrupt this interaction , potentially altering the kinase domain surface and affecting interactions with other molecules.To confirm these predicted changes , we performed in vitro kinase assays using cDNA constructs containing mutations suggestive of decreased kinase activity in both MAP3K5 ( E663K and I780F ) and MAP3K9 ( W333X and the previously described kinase dead mutation , K171A ) .