[Intramolecular mobility of pepsin]

Area of Science:

• Biochemistry
• Structural Biology
• Enzymology

Context:

• Pepsin, a key digestive enzyme, exhibits complex structural dynamics.
• Understanding protein flexibility is crucial for enzyme function.
• Previous studies focused on static pepsin structures.

Purpose:

• To investigate the dynamic structure and segmental flexibility of pepsin.
• To explore the relationship between protein flexibility and catalytic activity.
• To develop a dynamic model for pepsin structure.

Summary:

• Modified pepsin (aminopepsin) conjugated with a fluorescent label (DNS-Cl) retained catalytic activity.
• Fluorescence polarization measurements revealed lower rotational relaxation times than predicted for a rigid structure, indicating flexibility.
• Inhibitor binding and beta-mercaptoethanol treatment altered relaxation times, supporting intramolecular mobility.

Impact:

• A segmental model of dynamic pepsin structure was proposed, integrating experimental and X-ray data.
• The model provides insights into pepsinogen activation and the role of flexibility in pepsin's catalytic action.
• This research advances the understanding of enzyme dynamics and structure-function relationships.