C H A P T E R 3 5 , F IG U R E 8

Complementarity-determining regions. The actual locations of the complementarity-

determining regions of the VH and VL chains are shown in this fragment. The orientation is approximately 90° clock-

wise relative to the orientations in Figure 35-7. The CDR residues are primarily found in the hairpin turns that con-

nect the (3 sheets of the VH and VL domains. The crystallographic structure used for showing the CDR residues is

derived from the structure of a Fab fragment interacting with the capsular polysaccharide from

H . in flu en za e B

pub-

lished in the Protein Data Bank file 1HOU. The three orientations of the structure show (1) the backbone [3 sheets of

the immunoglobulin domain; (2) a side view that shows how the CDR regions overlap; and (3) a view that shows the

extensive area that the CDR regions provide for making contact with an epitope of the antigen. CDRl=red;

CDR2=green; CDR3=blue.

C H A P T E R 3 5 , F IG U R E 9

HIV-1 Gpl20 peptide bound to the anti-

gen recognition site of an antibody Fab fragment. The binding of HIV-1

Gpl20 residues 311-318 to the antigen binding site shows the actual

contacts between antigen and antibody that underlie Ag/Ab recognition.

The figure is derived from the coordinates published in the Protein Data

Bank file 1GGI.

C H A P T E R 3 5 , F IG U R E 1 0

Binding of protein G (

S . a u reu s)

to an Fc

fragment. Protein G binding mimics the Fc receptor binding of an Ig in the

Ig Fc region. Protein G is used for purification of antibodies and in their

“capture” in immunoassays. The figure is derived from the coordinates pub-

lished in the Protein Data Bank file 1FCC.