Figure 4.

(a). Mutations found in the clones selected from the yeast library are shown as yellow sticks. (b). The interaction between VH residue 72 and SEB(D99) was modeled. i. VH-Y72 (wild type) does not interact directly with SEB(D99), but ii. VH-Y72H, which is found in several selected mutants, may contribute to improved affinity by forming a hydrogen bond (dotted line). iii. VH-Y72R may stabilize the interaction further through electrostatic interaction. Minor adjustments of surface residues allow the formation of a network of salt bridges (dotted lines), involving VH-D50, VH-R72 and SEB(D99).