Bacterial glycoconjugates are natural ligands for the carbohydrate binding site of discoidin I and influence its cellular compartmentalization |
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Affiliation: | 1. Department of Biochemistry, Faculty of Sciences, University of Geneva, Science II, Geneva, Switzerland;2. Department of Biology/Chemistry, Division of Molecular Infection Biology, University of Osnabrück, Osnabrück, Germany |
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Abstract: | Klebsiella pneumoniae, Escherichia coli, and Bacillus subtilis, bacteria commonly eaten by Dictyostelium discoideum, contain glycoconjugates that bind discoidin I, a lectin synthesized by the slime mold as it differentiates. In cells fed bacteria that contain abundant discoidin I-binding glycoconjugates, these ligands and endogenous discoidin I accumulated in specialized structures called multilamellar bodies. In contrast, in cells fed bacteria that had been treated to thoroughly deplete them of discoidin I-binding glycoconjugates, neither endogenous discoidin I nor complementary glycoconjugates were found in the multilamellar bodies. In such cells discoidin I was located in the cytoplasm, as indicated by both immunohistochemistry with the electron microscope and immunoassay of subcellular fractions. The results indicate that a function of the carbohydrate-binding site of discoidin I is to interact with bacterial glycoconjugates, which the slime mold does not degrade. This interaction directs compartmentalization of the lectin in multilamellar bodies and its externalization from the cell in these structures. |
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