Toll-Like Receptor 4 Activation in Cancer Progression and Therapy
Figure 1
TLR4/MD-2 receptor complex recognizes and binds endotoxin. (a) MD-2 (shown in blue ribbons) is a soluble protein with a large hydrophobic pocket that directly binds bacterial endotoxin (red). One of the acyl chains of endotoxin (yellow) remains outside the hydrophobic pocket and mediates crucial interactions with TLR4 that bind the TLR4/MD-2 heterodimer together. Left: direct view of the MD-2 hydrophobic pocket. Right: side view showing the protruding endotoxin acyl chain. (b) The TLR4/MD-2/endotoxin heterodimer. Only the extracellular domains of TLR4 whose crystal structures were determined are shown [16].
