Fig. 4: Effect on PTP1B mechanism by D181, Q262 and C215 mutations.
From: Structure guided studies of the interaction between PTP1B and JAK
When substrate binds to wild-type PTP1B, C215 acts as an attacking nucleophile to form a cysteinyl-phosphate intermediate. Mutation of D181 (the general acid/base) and Q262 (which positions an attacking water molecule for hydrolysis of the cysteinyl-phosphate) slows the reaction rate by several orders of magnitude but do not entirely block cysteinyl-phosphate formation or its subsequent hydrolysis. These mutations also trap the phosphate and tyrosine products of the reaction in the active site, potentially by favouring the WPD loop in its closed conformation.
