An unusual dimeric structure and assembly for TLR4 regulator RP105–MD-1

Toll-like receptors (TLRs) recognize pathogens and initiate innate immune responses. TLR4 associates with adaptor molecule MD-2 to recognize LPS, and this complex is regulated by a homologous complex, RP105–MD-1. The crystal structure of RP105–MD-1 reveals a unique organization, suggesting a mechanism for regulation of TLR4 response to LPS.