Structural Characterization of Nanobodies during Germline Maturation

Area of Science:

• Biochemistry
• Structural Biology
• Immunology

Background:

• Camelid heavy-chain antibody variable domains (V_HH), or nanobodies, are small antibody fragments with significant therapeutic potential.
• Understanding the molecular mechanisms of nanobody-antigen interactions is crucial for therapeutic development.

Purpose of the Study:

• To structurally and dynamically characterize V_HH variants binding to hen egg-white lysozyme (HEL).
• To elucidate the conformational dynamics and thermodynamics governing the antigen-binding process in nanobodies.

Main Methods:

• Well-tempered metadynamics and molecular dynamics simulations were employed.
• Structural and dynamic characterization of four V_HH variants in complex with HEL.
• Kinetic characterization of paratope loop movements.

Main Results:

• Increased antibody affinity shifted state populations towards binding-competent conformations.
• Antigen-binding and stability contacts became less variable and more intense with higher affinity.
• Nanobodies demonstrated the conformational selection paradigm, with pre-existing binding-competent states.

Conclusions:

• Nanobody binding affinity is modulated by conformational selection and changes in paratope dynamics.
• Thermodynamic and kinetic analyses provide insights into nanobody-antigen interactions.
• These findings advance the understanding of nanobody mechanisms for therapeutic applications.