Fig. 4.

Binding of SSL3 to TLR2–lipid complexes. (A) Positioning of lipid head groups in the entrance to the TRL2 binding pocket: PC in the SSL3–TLR2 complex (Left), PE–DTPA in TLR2 (Center; PDB ID code 3A7C), Pam₂CSK₄ in TLR2–TLR6 complex (Right; TLR6 not shown, PDB ID code 3A79) (16). (B) Cross-sections of the SSL3–TLR2 surface near the lipopeptide pocket with ligands from A in stick representation: PC (blue, Left), PE–DTPA (gray, Left), and Pam₂CSK₄ (gray, Right). Binding of SSL3 in the presence of Pam₂CSK₄ would require a substantial conformational change of its head group as shown in the modeled Pam₂CSK₄ (blue, Right). (C) Native PAGE analysis of hTLR2 (panel 1) and hTLR2 complexes formed after incubation of hTLR2 (7 μM) with Pam₂CSK₄Rhodamine (20 μM; 18 h at 37 °C) and/or SSL3 (40 μM; 30 min at 20 °C) in the designated order (panels 2–5). Bands were visualized by rhodamine fluorescence (FL, red) and subsequent staining with Instant Blue (IB, blue).