. "Examination of the structure of Escherichia coli heat-labile enterotoxin in the AB5 complex at a resolution of 2.3A reveals that the doughnut-shaped B pentamer binds the enzymatic A subunit using a hairpin of the A2 fragment, through a highly charged central pore. Putative ganglioside GM1-binding sites on the B subunits are more than 20A removed from the membrane-crossing A1 subunit. This ADP-ribosylating (A1) fragment of the toxin has structural homology with the catalytic region of exotoxin A and hence also to diphtheria toxin." . . . "Nature" . "Kalk K.H." . "Hol W.G.J." . "Witholt B." . "Sixma T.K." . "Pronk S.E." . "Wartna E.S." . "van Zanten B.A.M." . "1991"^^ . "371-377" . "Crystal structure of a cholera toxin-related heat-labile enterotoxin from E. coli." . "351" . "doi:10.1038/351371a0" .