Antibody Elbow Angles are Influenced by their Light Chain Class

We have examined the elbow angles for 365 different Fab fragments, and observe that Fabs with λ light chains have adopted a wider range of elbow angles than their κ chain counterparts, and that the λ light chain Fabs are frequently found with very large (>195°) elbow angles. This apparent hyperflexibility of λ chain Fabs may be due to an insertion in their switch region, which is one residue longer than in κ chains, with glycine occurring most frequently at the insertion position. A new, web-based computer program that was used to calculate the Fab elbow angles is described.