Binds to the signaling molecule autoinducer 2 (AI-2), a furanosyl borate diester, (3a-methyl-5,6-dihydrofuro-[2,3d][1,3,2]dioxaborole-2,2,6,6a-tetraol). This complex then interacts with the LuxQ sensor protein. Belongs to the bacterial solute-binding protein 2 family.