How Coiled-Coil Assemblies Accommodate Multiple Aromatic Residues.

Area of Science:

• Protein engineering
• Structural biology
• Biochemistry

Background:

• Rational protein design relies on understanding amino acid contributions to protein folding.
• Alpha-helical coiled coils (CCs) are well-studied protein structures amenable to de novo design.
• Current CC design primarily uses aliphatic hydrophobic residues; the role of aromatic residues is less understood.

Purpose of the Study:

• To investigate the potential of tyrosine-rich sequences in forming CC structures.
• To determine the structural consequences and assembly patterns of tyrosine incorporation into CCs.
• To expand the design rules for CCs by exploring aromatic residue functionalities.

Main Methods:

• De novo design of tyrosine-rich sequences within a general CC-forming background.
• Experimental characterization of designed sequences to resolve new CC structures.
• Analysis of tyrosine residue positioning and interactions within the resolved structures.

Main Results:

• Successfully designed and resolved novel CC structures incorporating tyrosine-rich sequences.
• Identified an antiparallel tetramer where tyrosine residues are solvent-accessible at the core-surface interface.
• Discovered a more complex CC structure with buried tyrosine residues forming extensive hydrogen-bond networks.

Conclusions:

• Tyrosine-rich sequences can form alpha-helical coiled coils, leading to diverse structural assemblies.
• Tyrosine residues can be strategically positioned at CC interfaces, either solvent-accessible or buried.
• The findings provide new insights into incorporating aromatic residues for functionalizing CC structures.