Epitope-dependent thermodynamic signature of single-domain antibodies against hen egg lysozyme.

A substantial body of work has been carried out describing the structural features of the complex between single-domain antibodies (VHHs) and antigens, and the preeminence for epitopes located at concave surfaces of the antigen. However, the thermodynamic basis of binding is far less clear. Here, we have analysed the energetic profiles of five VHHs binding to the catalytic cleft or to a noncleft epitope of hen egg lysozyme. Various binding energetic profiles with distinctive enthalpic/entropic contributions and structural distribution of critical residues were found in the five antibodies analysed. Collectively, we suggest that from an energetic point of view the binding mechanism is influenced by the shape of the epitope. This information may be beneficial for the design of tailored epitopes for VHHs and their practical use.