Figure 3. Interface histidines and pH dependence of TC-CD320 affinity.

(a) Histidine residues identified at the TC-CD320 interface: CD320 (yellow and gold) and TC (blue) are shown as backbone traces, with histidine residues at the binding interface shown as respectively coloured sticks. (b) SDS–polyacrylamide gel electrophoresis (SDS–PAGE) showing TC dissociation from an immobilized CD320_AVI-TC complex at pH 4.8 but not at pH 7.5. Two successive washes (A and B) are shown. (c) TC-CD320 binding curves at pH 4.8 and 7.5 obtained from solid-phase binding experiments (n=5, error bars indicate s.d.).