Antibody elbow angles are influenced by their light chain class

Area of Science:

• Structural biology
• Immunology
• Computational biology

Background:

• Antibody fragments (Fabs) are crucial in immunology and therapeutics.
• Understanding Fab flexibility is key to antibody engineering.
• Previous studies have not fully characterized differences in Fab elbow angles based on light chain type.

Purpose of the Study:

• To investigate and compare the elbow angles of antibody Fab fragments with lambda versus kappa light chains.
• To identify structural features that may explain observed differences in flexibility.

Main Methods:

• Analysis of 365 antibody Fab fragments.
• Calculation of Fab elbow angles using a novel web-based computer program.
• Comparison of angle distributions between lambda and kappa light chain Fabs.

Main Results:

• Fab fragments with lambda light chains display a wider range of elbow angles compared to kappa chain counterparts.
• Lambda chain Fabs are frequently observed with large elbow angles (>195 degrees).
• A one-residue insertion in the switch region, often containing glycine, is noted in lambda chain Fabs and may contribute to hyperflexibility.

Conclusions:

• Lambda light chains are associated with increased Fab elbow angle flexibility.
• A switch region insertion is a potential structural basis for this observed hyperflexibility.
• The developed computational tool facilitates the study of antibody fragment conformations.