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Mapping the interface between calmodulin and MARCKS-related protein by fluorescence spectroscopy
A Ulrich1, A A Schmitz, T Braun
1Department of Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland.
Summary
MARCKS-related protein (MRP) binds calmodulin (CaM) via its effector domain. Tryptophan engineering revealed specific domain interactions and suggested lipid moiety involvement in MRP-CaM binding.
Area of Science:
- Biochemistry
- Structural Biology
- Molecular Interactions
Background:
- MARCKS-related protein (MRP) is a myristoylated protein kinase C substrate.
- MRP exhibits high-affinity binding to calmodulin (CaM).
- Structural insights into MRP-CaM interactions are limited.
Purpose of the Study:
- To elucidate the structural basis of MRP-CaM binding.
- To investigate the role of the effector domain in MRP-CaM complex formation.
- To determine the contribution of the N-terminal lipid moiety to binding.
Main Methods:
- Site-directed mutagenesis to introduce 10 tryptophan residues into the MRP effector domain.
- Fluorescence spectroscopy to monitor environmental changes and binding.
- Intermolecular fluorescence quenching using selenomethionine-labeled CaM.
- Comparison of myristoylated and unmyristoylated MRP constructs.
Main Results:
- The MRP effector domain resides in a polar environment in free MRP, suggesting a rod-like structure.
- Tryptophan fluorescence changes confirmed effector domain participation in CaM binding.
- Residue-specific quenching indicated antiparallel domain interactions between MRP and CaM.
- Myristoylation at the N-terminus influences MRP-CaM complex formation.
Conclusions:
- The effector domain of MRP adopts a specific conformation and interacts with both CaM domains.
- The N-terminal lipid modification plays a role in the overall MRP-CaM binding interface.
- This study provides critical structural details of a key protein-protein interaction.