Figure 2.

Antibody 57-2 mutations. In all the figures, the heavy-chain is colored purple; the light-chain, brown. The side chains of the important residues are drawn. For the other parts of the protein, only the Cα-trace or the backbone heavy atoms are shown, if not mentioned. (A) The variable domain and a part of the constant domain of the antibody 57-2. The estradiol molecule and the side chains of light-chain wild-type residues targeted by point mutations are shown. The tip of the heavy-chain CDR2 targeted by a four-amino-acid insertion is shown as cyan. (B) The insertion site in CDR2 of heavy-chain. The insertion was introduced between the residues labeled with purple balls. Only the Cα-atoms are shown, except for the tryptophans W50^H and W95^H, for which side chains are also shown. (C) Mutation N50^LY. The side chain of the mutated residue is shown and the lettering of the steroid rings is indicated. (D) Mutation F91^LY. The dotted lines represent hydrogen bonds. (E) Mutation F83^LS. The van der Waals surface of the side chain of Phe83^L replaced by the mutation is indicated with white dots. The blue surface shows the volume occupied by the hydrophobic side chains of the residues situated in the vicinity of the residue 83^L. The light-chain constant domain atoms are drawn as CPK-models, whereas for the variable domain only Cα-trace or the backbone heavy atoms is shown. (F) The double mutation N50^LY and F91^LY. The white lines represent the close contacts (∼2.7 to 3.1 Å) between the ηOH of Tyr91^L and the aromatic carbons of Tyr50^L.