title: Pathogenesis of Shigella diarrhea: rabbit intestinal cell microvillus membrane binding site for Shigella toxin.
abstract: This study examined the binding of purified 125I-labeled shigella toxin to rabbit jejunal microvillus membranes (MVMs). Toxin binding was concentration dependent, saturable, reversible, and specifically inhibited by unlabeled toxin. The calculated number of toxin molecules bound at 4 degrees C was 7.9 X 10(10) (3 X 10(10) to 2 X 10(11))/micrograms of MVM protein or 1.2 X 10(6) per enterocyte. Scatchard analysis showed the binding site to be of a single class with an equilibrium association constant, K, of 4.7 X 10(9) M-1 at 4 degrees C. Binding was inversely related to the temperature of incubation. A total of 80% of the labeled toxin binding at 4 degrees C dissociated from MVM when the temperature was raised to 37 degrees C, but reassociated when the temperature was again brought to 4 degrees C. There was no structural or functional change of MVM due to toxin as monitored by electron microscopy or assay of MVM sucrase activity. These studies demonstrate a specific binding site for shigella toxin on rabbit MVMs. The physiological relevance of this receptor remains to be determined.
mesh_terms: D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism; D004405:Dysentery, Bacillary / Q000209:etiology*; D006367:HeLa Cells / Q000032:analysis; D006801:Humans; D066298:In Vitro Techniques; D007422:Intestines / Q000032:analysis* / Q000187:drug effects; D007457:Iodine Radioisotopes; D008871:Microvilli / Q000032:analysis; D011817:Rabbits; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic / Q000032:analysis*; D022603:Shiga Toxins; D013696:Temperature
chemical_list: D001427:Bacterial Toxins; D007457:Iodine Radioisotopes; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D022603:Shiga Toxins; C045390:shigella toxin receptor