Association of the anti-hen egg lysozyme antibody HyHEL-5 with avian species variant and mutant lysozymes

The energetics of association of the murine anti-hen egg lysozyme antibody HyHEL-5 with bobwhite quail lysozyme, California quail lysozyme, and the Arg45-->Lys mutant of hen egg lysozyme was characterized by isothermal titration calorimetry. The association of each lysozyme with HyHEL-5 is enthalpically driven in the temperature range 10 degrees C to 37 degrees C. The calorimetric results indicate that the salt-links between Arg45 and Arg68 of hen egg lysozyme and GluH50 on the HyHEL-5 paratope are energetically important in HyHEL-5/HEL association. In contrast to previous studies, the results suggest that the three characteristic 'quail' mutations affect the energetics of antibody/antigen association, even though they are buried and not in direct contact with the antibody.