Structural Basis for Species Selectivity in the HIV-1 gp120-CD4 Interaction: Restoring Affinity to gp120 in Murine CD4 Mimetic Peptides

Figure 4

Intrinsic stability and gp120-interaction of the mCD4 peptide core. (a) Scheme of intra- and intermolecular hydrogen bonds and analyzed distances and torsion angles. Measured distances are marked d1–d7. Residues selected for torsion analysis are highlighted. (b) Dihedral angles of residues V44 to R47 are shown as a function of time. φ angle (C_i−1-N_i-C_i ^α-C_i) in black, ψ angle (N_i-C_i ^α-C_i-N_i+1) in gray. Distances were measured between main chain hydrogen donor and acceptor atoms. (c) Zoom into the interface and comparison of the two interfaces mCD4-peptide-gp120 and hCD4-gp120 (1RZJ). Overlay of a representative snapshot after 90 ns onto crystal structure of the gp120-hCD4 complex. Fit on residues 362–369 of β15. mCD4-peptide and hCD4-protein are colored in green and gray, respectively. (d) Hydrogen bond distances between β-strands C/C′ and C′/C″ and intermolecular hydrogen bond distances between C″ and β15.