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Atomic structure of a tryptophan-zipper pentamer
Jie Liu1, Wei Yong, Yiqun Deng
1Department of Biochemistry, Weill Medical College of Cornell University, New York, NY 10021, USA.
Summary
Engineered a "Trp-zipper" protein using tryptophan residues to form a stable alpha-helical pentamer. This study reveals novel coiled-coil interactions and a unique axial channel, expanding protein engineering insights.
Area of Science:
- Biochemistry
- Structural Biology
- Protein Engineering
Background:
- Coiled-coil motifs mediate protein-protein interactions via alpha-helical chains.
- Hydrophobic seams at 'a' and 'd' positions, typically aliphatic, drive helix association.
Purpose of the Study:
- To investigate the potential of aromatic residues, specifically tryptophan (Trp), in promoting coiled-coil formation.
- To engineer and characterize a novel protein structure utilizing Trp residues.
Main Methods:
- Engineering a "Trp-zipper" protein with Trp at all interfacial positions.
- Structural analysis using X-ray crystallography at 1.45-Å resolution.
- Characterization of the protein's stability and assembly in aqueous solution.
Main Results:
- Formation of a stable, discrete, alpha-helical pentamer in water at physiological pH.
- Determination of a parallel, five-stranded coiled coil structure.
- Discovery of a novel "knobs-into-holes" packing involving Trp side chains.
- Identification of an ~8-Å axial channel lined with indole rings, filled with PEG 400, water, and sulfate ions.
Conclusions:
- Engineered Trp-zipper pentamer expands understanding of coiled-coil assembly and molecular recognition.
- Demonstrates the feasibility of using aromatic residues for protein structure engineering.
- Suggests potential applications as a soluble model for membrane ion channels.