Structural characterization of a beta-turn mimic within a protein-protein interface

Area of Science:

• Protein Engineering
• Structural Biology
• Biochemistry

Background:

• Beta-turns (β-turns) are crucial secondary structures in proteins, found on surfaces and within protein-protein interfaces.
• Current protein engineering focuses on surface-exposed loop mimics, overlooking buried turn functionalities.

Purpose of the Study:

• To investigate the potential of the synthetic β-turn mimic, Hot═Tap, for both backbone and side-chain mimicry in protein design.
• To evaluate Hot═Tap's ability to induce and stabilize β-turns within complex protein structures.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy to assess the turn-inducing capability of Hot═Tap in cyclic hexapeptides.
• X-ray crystallography of a fibritin-foldon/Hot═Tap hybrid to determine structural interactions at atomic resolution.

Main Results:

• NMR studies confirmed Hot═Tap's strong β-turn-inducing properties.
• Crystallography revealed Hot═Tap's ability to replace a βI'-turn with a βII'-type structure in a protein interface.
• Hot═Tap participates in direct and water-mediated interactions within the protein trimer interface.

Conclusions:

• Hot═Tap is a versatile β-turn mimic with both backbone and side-chain mimicking capabilities.
• This mimicry facilitates adaptation to complex protein environments and protein-protein interfaces.
• Hot═Tap holds promise for simplifying the design of novel synthetic proteins.