Negative Regulation of Peptidyl-Prolyl Isomerase Activity by Interdomain Contact in Human Pin1

Pin1 is a modular peptidyl-prolyl isomerase specific for phosphorylated Ser/Thr-Pro (pS/T-P) motifs, typically within intrinsically disordered regions of signaling proteins. Pin1 consists of two flexibly linked domains: an N-terminal WW domain for substrate binding and a larger C-terminal peptidyl-prolyl isomerase (PPIase) domain. Previous studies showed that binding of phosphopeptide substrates to Pin1 could alter Pin1 interdomain contact, strengthening or weakening it depending on the substrate sequence. Thus, substrate-induced changes in interdomain contact may act as a trigger within the Pin1 mechanism. Here, we investigate this possibility via nuclear magnetic resonance studies of several Pin1 mutants. Our findings provide new mechanistic insights for those substrates that reduce interdomain contact. Specifically, the reduced interdomain contact can allosterically enhance PPIase activity relative to that when the contact is sustained. These findings suggest Pin1 interdomain contact can negatively regulate its activity. [Display omitted] •Investigated interplay between interdomain contact and activity in Pin1•Studied Pin1 mutants that perturb interdomain contacts or substrate interaction•Reduced interdomain contact yields enhanced isomerase activity•Results suggest interdomain contact can allosterically regulate Pin1 activity Pin1 is a two-domain cell cycle enzyme that catalyzes the cis-trans isomerization of phospho-S/T-P motifs. Wang et al. use NMR to examine Pin1 mutants and reveal a phosphopeptide substrate that reduces interdomain contact while enhancing isomerase activity; this suggests negative allosteric regulation of the catalytic site by interdomain contact.