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MD-1 and MD-2 are cofactors required for LPS signaling through cell surface receptors. MD-2 and its binding partner, Toll-like receptor 4 (TLR4), are essential for the innate immune responses of mammalian cells to bacterial lipopolysaccharide (LPS); MD-2 directly binds the lipid A moiety of LPS. The TLR4-like receptor, RP105, which mediates LPS-induced lymphocyte proliferation, interacts with MD-1; MD-1 enhances RP105-mediated LPS-induced growth of B cells. These proteins belong to the ML domain family.
Jiyao W et al.(2023). "The conserved domain database in 2023.",