Characterization of the ganglioside recognition profile of Escherichia coli heat-labile enterotoxin LT-IIc

• The heat-labile enterotoxins of Escherichia coli and cholera toxin of Vibrio cholerae are related in structure and function. Each of these oligomeric toxins is comprised of one A polypeptide and five B polypeptides. The B-subunits bind to gangliosides, which are followed by uptake into the intoxicated cell and activation of the host's adenylate cyclase by the A-subunits. There are two antigenically distinct groups of these toxins. Group I includes cholera toxin and type I heat-labile enterotoxin of E. coli; group II contains the type II heat-labile enterotoxins of E. coli. Three variants of type II toxins, designated LT-IIa, LT-IIb and LT-IIc have been described. Earlier studies revealed the crystalline structure of LT-IIb. Herein the carbohydrate binding specificity of LT-IIc B-subunits was investigated by glycosphingolipid binding studies on thin-layer chromatograms and in microtiter wells. Binding studies using a large variety of glycosphingolipids showed that LT-IIc binds with high affinity to gangliosides with a terminal Neu5Ac alpha 3Gal or Neu5Gc alpha 3Gal, e.g. the gangliosides GM3, GD1a and Neu5Ac alpha 3-/Neu5Gc alpha 3--neolactotetraosylceramide and Neu5Ac alpha 3-/Neu5Gc alpha 3-neolactohexaosylceramide. The crystal structure of LT-IIc B-subunits alone and with bound LSTd/sialyl-lacto-N-neotetraose d pentasaccharide uncovered the molecular basis of the ganglioside recognition. These studies revealed common and unique functional structures of the type II family of heat-labile enterotoxins.

Ämnesord

NATURVETENSKAP  -- Biologi -- Biokemi och molekylärbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Biochemistry and Molecular Biology (hsv//eng)

Nyckelord

b-subunit crystal structure

B-subunit

carbohydrate binding

ganglioside recognition

heat-labile enterotoxin LT-IIc

normal human-leukocytes

leukemia hl60 cells

binding specificities

cholera-toxin

structural-characterization

e-selectin

receptors

monosialogangliosides

determinants

etiology

Biochemistry & Molecular Biology

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