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Updated: Mar 22, 2026

Studies of Chaperone-Cochaperone Interactions using Homogenous Bead-Based Assay
Published on: July 21, 2021
Conformational Heterogeneity of Cyclosporin A in Cyclophilin 18 Binding
Weilin Lin1, Andres Quintero1, Yixin Zhang1
1B CUBE Center for Molecular Bioengineering, Technische Universität Dresden, Arnoldstrasse 18, 01307 Dresden, Germany.
Abstract:
The immunosuppressive drug cyclosporin A (CsA) binds to its receptor protein cyclophilin 18 (Cyp18) in two distinct kinetic phases, while the mechanism remains elusive. Stopped-flow measurements coupled with titration and competition experiments were used to investigate the puzzling two-phase process of CsA and Cyp18 interaction. This study leads to the dissection of different conformational fractions of either direct fast binding or slow binding with rate-limiting conformational inter-conversion and the real-time measurement of kon value (8.34 ± 0.22 x106 M-1s-1) in solution. Furthermore, our study indicates that the structure of CsA during dissociation from the protein possesses a distribution of conformations different from those in solution under equilibrium condition.
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