Cavities of alpha(1)-antitrypsin that play structural and functional roles

Area of Science:

• Biochemistry
• Structural Biology
• Protein Dynamics

Background:

• Serine protease inhibitors (serpins) possess a strained native conformation essential for their function.
• Alpha(1)-antitrypsin (AAT) is a prototype serpin, and its strain is linked to internal cavities.
• Cavities within AAT contribute to its structural stability and inhibitory activity.

Purpose of the Study:

• To systematically map cavities in AAT that influence its native strain and function.
• To investigate the role of cavity-filling mutations in stabilizing AAT's conformation.
• To correlate cavity environment flexibility with stabilization effects and inhibitory activity.

Main Methods:

• Design and implementation of cavity-filling mutations in AAT residues.
• Energetic analysis of cavity filling and protein stabilization.
• Assessment of inhibitory activity of mutated AAT variants.

Main Results:

• Energetically unfavorable cavities are present throughout the AAT molecule.
• Cavity-filling mutations stabilized the native AAT conformation at 80% of tested sites.
• Stabilization effects varied based on cavity environment flexibility; mutations near beta-sheet A reduced inhibitory activity.

Conclusions:

• Internal cavities are critical structural determinants of AAT's native strain and stability.
• Targeted cavity filling can stabilize AAT, but strategic placement is key to maintaining inhibitory function.
• Cavity-filling mutations impacting beta-sheet A suggest its dynamic role in protease complex formation.