Regulation of Pin1 peptidyl-prolyl cis/trans isomerase activity by its WW binding module on a multi-phosphorylated peptide of Tau protein

The WW module of the peptidyl-prolyl cisltrans isomerase Pint targets specifically phosphorylated proteins involved in the cell cycle through the recognition of phospho-Thr(Ser)-Pro motifs. When the microtubulle-associated Tau protein becomes hyperphosphorylated, it equally becomes a substrate for Pint, with two recognition sites described around the phosphorylated Thr212 and Thr231. The Pint WW domain binds both sites with moderate affinity, but only the Thr212-Pro213 bond is isomerized by the catalytic domain of Pint. We show here that, in a peptide carrying a single recognition site, the WW module increases significantly the enzymatic isomerase activity of Pint. However, with addition of a second recognition motif, the affinity of both the WW and catalytic domain for the substrate increases, but the isomerization efficacy decreases. We therefore conclude that the WW domain can act as a negative regulator of enzymatic activity when multiple phosphoryllation is present, thereby suggesting a subtle mechanism of its functional regulation. (c) 2005 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.