The crystal structure of LsrB from Yersinia pestis complexed with autoinducer-2 (AI-2; space group P2(1)2(1)2(1), unit-cell parameters a = 40.61, b = 61.03, c = 125.23 Å) has been solved by molecular replacement using the structure of LsrB from Salmonella typhimurium (PDB entry 1tjy) and refined to R = 0.180 (R(free) = 0.213) at 1.75 Å resolution. The electron density for bound AI-2 and the stereochemistry of the AI-2-binding site are consistent with bound AI-2 adopting the (2R,4S)-2-methyl-2,3,3,4-tetrahydroxytetrahydrofuran conformation, just as has been observed in the crystal structures of the Salmonella typhimurium and Sinorhizobium meliloti LsrB-AI-2 complexes.