Protein engineering and NMR studies of calmodulin

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Calmodulin (CaM) is a calcium-binding protein that regulates numerous enzymes and proteins.
• CaM possesses a dumbbell-shaped structure with two domains linked by a flexible region.
• CaM binds to distinct 20-residue calmodulin-binding domains in target proteins, despite lacking sequence homology.

Purpose of the Study:

• To elucidate the structural and chemical features of CaM that enable its promiscuous binding to diverse protein targets.
• To investigate the role of methionine-rich hydrophobic surfaces and the flexible linker in CaM's binding capabilities.
• To analyze the structural basis of CaM-protein interactions using biophysical techniques.

Main Methods:

• Analysis of CaM's structural features, including methionine-rich hydrophobic surfaces and flexible linkers.
• Characterization of enzyme activation by Met --> Leu mutants of CaM.
• Utilizing Nuclear Magnetic Resonance (NMR) and spectroscopic experiments to determine CaM-bound peptide structures.
• Structural analysis of synthetic peptides containing CaM-binding domains.

Main Results:

• Methionine-rich hydrophobic surfaces provide a malleable and sticky interface for binding various hydrophobic peptides.
• Mutations in methionine residues affect CaM's enzyme activation properties.
• CaM-bound peptides adopt an alpha-helical structure and interact via amino acid sidechains.
• The flexible linker region contributes to CaM's binding versatility.

Conclusions:

• CaM's promiscuity arises from its adaptable hydrophobic surfaces and flexible structure.
• Protein-protein interactions with CaM, mediated by sidechain interactions in alpha-helical peptides, are unique.
• These unique binding characteristics underpin CaM's ability to regulate a wide array of distinct protein partners.