Ligand-dependent equilibrium fluctuations of single calmodulin molecules

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Item Type:	Article
Title:	Ligand-dependent equilibrium fluctuations of single calmodulin molecules
Creators Name:	Junker, J.P., Ziegler, F. and Rief, M.
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.
Keywords:	Atomic Force Microscopy, Calcium, Calmodulin, Kinetics, Ligands, Monte Carlo Method, Myosin-Light-Chain Kinase, Peptide Fragments, Peptides, Protein Binding, Protein Conformation, Protein Folding, Tertiary Protein Structure, Thermodynamics, Wasp Venoms
Source:	Science
ISSN:	0036-8075
Publisher:	American Association for the Advancement of Science
Volume:	323
Number:	5914
Page Range:	633-637
Date:	30 January 2009
Official Publication:	https://doi.org/10.1126/science.1166191
PubMed:	View item in PubMed

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