FIGURE 4.

Model of CD4mim variants with alterations indicated. A, CD4mim1 is a natural amino acid form of CD4M33, a CD4-mimetic peptide built from a scorpion toxin scaffold, with three disulfide bonds. Residues held constant during the library construction are indicated in blue. For CD4mim2, cysteines 1 and 19 were altered to glycine and leucine, respectively, shown in red. CD4mim4, the product of the first cycle of phage selection and the template the second phage library has eight total differences from CD4mim1, again indicated in red (see Fig. 2B for changes). CD4mim6, the final product of the second cycle, has 12 such differences. B, CD4mim6 modeled into the CD4 binding site of HIV-1 gp120. All models are based on the Protein Data Bank structure 1YYM by Huang et al. (20) and generated with the PyMOL mutagenesis tool.