N-terminal β-strand swapping in a consensus-derived alternative scaffold driven by stabilizing hydrophobic...

Area of Science:

• Protein crystallography
• Structural biology
• Biochemistry

Background:

• Tenascin Fibronectin type III (FN3) domains are versatile protein scaffolds.
• Alternative scaffolds can exhibit unique structural features like N-terminal beta-strand swapping.
• Understanding the structural basis of scaffold stability is crucial for protein engineering.

Purpose of the Study:

• To determine the crystal structure of an N-terminal beta-strand-swapped tenascin FN3 alternative scaffold.
• To compare the swapped structure with its unswapped counterpart.
• To elucidate the structural driving forces behind N-terminal beta-strand swapping and dimer formation.

Main Methods:

• X-ray crystallography to determine high-resolution structures.
• Structural comparison and analysis of protein-protein interactions.
• Analysis of hydrophobic core packing and surface burial.

Main Results:

• The crystal structure of the N-terminal beta-strand-swapped tenascin FN3 scaffold was determined.
• Residue F88 shows altered orientation and tighter packing within the hydrophobic core in the swapped structure.
• Dimer formation leads to the burial of a significant hydrophobic surface patch.

Conclusions:

• Tighter packing of F88 and burial of surface hydrophobicity are key driving forces for N-terminal beta-strand swapping.
• These interactions stabilize the formation of a compact dimer.
• The findings provide insights into the design principles for stable protein alternative scaffolds.