Complete Determination of the Pin1 Catalytic Domain Thermodynamic Cycle by NMR Lineshape Analysis

Authors

Alexander I. Greenwood, Cornell University
Monique J. Rogals, Cornell University
Soumya De, Cornell University
Kun Ping LuFollow
Evgueni Kovriguine, Marquette UniversityFollow
Linda K. Nicholson, Cornell UniversityFollow

Document Type

Article

Publication Date

9-2011

Source Publication

Journal of Biomolecular NMR

Source ISSN

0925-2738

Abstract

The phosphorylation-specific peptidyl-prolyl isomerase Pin1 catalyzes the isomerization of the peptide bond preceding a proline residue between cis and trans isomers. To best understand the mechanisms of Pin1 regulation, rigorous enzymatic assays of isomerization are required. However, most measures of isomerase activity require significant constraints on substrate sequence and only yield rate constants for the cis isomer, k^cis_catand apparent Michaelis constants, K^App_M . By contrast, NMR lineshape analysis is a powerful tool for determining microscopic rates and populations of each state in a complex binding scheme. The isolated catalytic domain of Pin1 was employed as a first step towards elucidating the reaction scheme of the full-length enzyme. A 24-residue phosphopeptide derived from the amyloid precurser protein intracellular domain (AICD) phosphorylated at Thr668 served as a biologically-relevant Pin1 substrate. Specific ¹³C labeling at the Pin1-targeted proline residue provided multiple reporters sensitive to individual isomer binding and on-enzyme catalysis. We have performed titration experiments and employed lineshape analysis of phosphopeptide ¹³C–¹H constant time HSQC spectra to determine k^cis_cat , k^trans_cat , K^cis_D , and K^trans_D for the catalytic domain of Pin1 acting on this AICD substrate. The on-enzyme equilibrium value of [E·trans]/[E·cis] = 3.9 suggests that the catalytic domain of Pin1 is optimized to operate on this substrate near equilibrium in the cellular context. This highlights the power of lineshape analysis for determining the microscopic parameters of enzyme catalysis, and demonstrates the feasibility of future studies of Pin1-PPIase mutants to gain insights on the catalytic mechanism of this important enzyme.

Comments

Accepted version. Journal of Biomolecular NMR, Vol. 51, No. 1-2 (September 2011): 21-34. DOI: © 2011 Springer Science+Business Media B.V. Used with permission.

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Recommended Citation

Greenwood, Alexander I.; Rogals, Monique J.; De, Soumya; Lu, Kun Ping; Kovriguine, Evgueni; and Nicholson, Linda K., "Complete Determination of the Pin1 Catalytic Domain Thermodynamic Cycle by NMR Lineshape Analysis" (2011). Chemistry Faculty Research and Publications. 244.
https://epublications.marquette.edu/chem_fac/244