Understanding how Pin1-substrate interactions modulate affinity and inter-domain dynamics

Tuesday, October 16, 2018

Dinusha Jinasena

Department of Chemistry

Mississippi State University

Dissertation Defense

2:00 p.m. -- Library Auditorium

Pin1 is an essential Peptidyl-prolyl isomerase (PPIase) that catalyzes cis-trans prolyl isomerization in proteins containing pSer/Thr-Pro motifs. It has an N-terminal WW domain and a C-terminal PPIase domain. Pin1 targets pSer/Thr-Pro motifs by its WW binding domain and catalyzes isomerization through its PPIase domain.
This research is focused on elucidating the interactions between Pin1/substrate, the inter-domain dynamics upon binding, and the catalytic activity of Pin1 upon binding different substrates. Specifically, we investigated the Pin1-Histone H1 interaction and designed a series of chimeric peptides based on the H1.4 sequence (KATGAApTPKKSAKW). NMR titrations were performed for each peptide using both full-length Pin1 as well as the WW domain alone, to analyze the binding affinities (KD). 15N relaxation and residual dipolar couplings (RDCs) were used to monitor the degree to which peptide binding induced inter-domain interactions. We also investigated whether our chimeric sequences could alter catalysis (kex) using 1H-1H EXSY NMR experiments. Finally, when combined with molecular modeling, our results suggest a structural basis for how substrate binding can alter Pin1 inter-domain dynamics.

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