Fig. 5: Structures of the acceptor and ternary complexes.

a, b Orthogonal views of the electron density (2mFo-DFc map contoured at 1.0 σ) for the acceptor bound in the WbbBGT99 active site. c Details of the interactions mediated by the acceptor in the active site. d Electron density for the ternary complex, contoured around Cys232, Kdo, and the acceptor (2mFo-DFc map contoured at 1.0 σ). e Details of the ternary complex structure. Neither the donor nor acceptor shifts appreciably from their respective binary complexes, and the donor and acceptor interact extensively. This complex places the O3 hydroxyl group of rhamnose within 3.6 Å of the anomeric carbon of Kdo (marked with an asterisk) and in line with the Kdo(C2)–C232Sγ bond.