Ligand-dependent equilibrium fluctuations of single calmodulin molecules

Jan Philipp Junker, Fabian Ziegler, Matthias Rief

Research output: Contribution to journalArticlepeer-review

184 Scopus citations

Abstract

Single-molecule force spectroscopy allows superb mechanical control of protein conformation. We used a custom-built low-drift atomic force microscope to observe mechanically induced conformational equilibrium fluctuations of single molecules of the eukaryotic calcium-dependent signal transducer calmodulin (CaM). From this data, the ligand dependence of the full energy landscape can be reconstructed. We find that calcium ions affect the folding kinetics of the individual CaM domains, whereas target peptides stabilize the already folded structure. Single-molecule data of full length CaM reveal that a wasp venom peptide binds noncooperatively to CaM with 2:1 stoichiometry, whereas a target enzyme peptide binds cooperatively with 1:1 stoichiometry. If mechanical load is applied directly to the target peptide, real-time binding/unbinding transitions can be observed.

Original languageEnglish
Pages (from-to)633-637
Number of pages5
JournalScience
Volume323
Issue number5914
DOIs
StatePublished - 30 Jan 2009

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