Resolving dual binding conformations of cellulosome cohesin-dockerin complexes using single-molecule force spectroscopy
- Ludwig-Maximilians-Universität München, Germany
- Kean University, United States
- Weizmann Institute of Science, Israel
Abstract
Receptor-ligand pairs are ordinarily thought to interact through a lock and key mechanism, where a unique molecular conformation is formed upon binding. Contrary to this paradigm, cellulosomal cohesin-dockerin (Coh-Doc) pairs are believed to interact through redundant dual binding modes consisting of two distinct conformations. Here, we combined site-directed mutagenesis and single-molecule force spectroscopy (SMFS) to study the unbinding of Coh:Doc complexes under force. We designed Doc mutations to knock out each binding mode, and compared their single-molecule unfolding patterns as they were dissociated from Coh using an atomic force microscope (AFM) cantilever. Although average bulk measurements were unable to resolve the differences in Doc binding modes due to the similarity of the interactions, with a single-molecule method we were able to discriminate the two modes based on distinct differences in their mechanical properties. We conclude that wild-type Doc from Clostridium thermocellum exocellulase Cel48S populates each binding mode with equal probability.
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© 2015, Jobst et al.
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Resolving dual binding conformations of cellulosome cohesin-dockerin complexes using single-molecule force spectroscopy
eLife 4:e10319.
https://doi.org/10.7554/eLife.10319
