Figure 4. Representative binding pose of a Cu²⁺–FLK complex at the surface of PBP1B, illustrating steric exclusion from the transglycosylase groove.The Cu²⁺-complexed peptide (stick representation) fails to penetrate the narrow hydrophobic binding groove preferred by uncomplexed FLK peptides and instead remains superficially associated with the protein surface (electrostatic surface rendering: red, negative; blue, positive; white, neutral). Metal coordination increases steric bulk and alters charge distribution, preventing productive insertion into the catalytic cleft and resulting in a sparse interaction network relative to uncomplexed peptides. This provides a structural rationale for the catastrophic loss of PBP1B affinity observed upon Cu²⁺ complexation : Docking-Based Evaluation of Defensin-Derived Peptides and Their Cu²⁺ Complexes as Dual-Target Inhibitors of Exo-β-(1,3)-Glucanase and Penicillin-Binding Protein Transglycosidase 1B : Science and Education Publishing

Figure 4. Representative binding pose of a Cu²⁺–FLK complex at the surface of PBP1B, illustrating steric exclusion from the transglycosylase groove.The Cu²⁺-complexed peptide (stick representation) fails to penetrate the narrow hydrophobic binding groove preferred by uncomplexed FLK peptides and instead remains superficially associated with the protein surface (electrostatic surface rendering: red, negative; blue, positive; white, neutral). Metal coordination increases steric bulk and alters charge distribution, preventing productive insertion into the catalytic cleft and resulting in a sparse interaction network relative to uncomplexed peptides. This provides a structural rationale for the catastrophic loss of PBP1B affinity observed upon Cu²⁺ complexation

American Journal of Pharmacological Sciences. 2026, 14(1), 7-19 doi:10.12691/ajps-14-1-2