Structural and functional changes associated with cyanogen bromide treatment of wheat germ agglutinin

Balasubramaniam, Nandha Kumar; Czapla, T.H.; Rao, A. Gururaj

doi:10.1016/0003-9861(91)90209-2

Cited by 9 publications

(5 citation statements)

References 35 publications

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“…3 B, the acid monomer is somewhat expanded, showing an apparent molecular mass of 22 5 2 kDa (versus the expected 17.1 kDa), whereas the corresponding value for the dimer at higher pH values averaged 33.7 kDa. On the other hand, the far-CD spectrum varied somewhat in the negative band centered at~205 nm, as similarly observed in cleaved WGA (25). As can be seen in Fig.…”

Section: Unfolding Of Monomeric Wgasupporting

confidence: 76%

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Folding and Homodimerization of Wheat Germ Agglutinin

Portillo-Téllez

Bello

Salcedo

et al. 2011

Biophysical Journal

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Wheat germ agglutinin (WGA) is emblematic of proteins that specialize in the recognition of carbohydrates. It was the first lectin reported to have a capacity for discriminating between normal and malignant cells. Since then, it has become a preferred model for basic research and is frequently considered in the development of biomedical and biotechnological applications. However, the molecular basis for the structural stability of this homodimeric lectin remains largely unknown, a situation that limits the rational manipulation and modification of its function. In this work we performed a thermodynamic characterization of WGA folding and self-association processes as a function of pH and temperature by using differential scanning and isothermal dilution calorimetry. WGA is monomeric at pH 2, and one of its four hevein-like domains is unfolded at room temperature. Under such conditions, the agglutinin exhibits a fully reversible thermal unfolding that consists of three two-state transitions. At higher pH values, the protein forms weak, nonobligate dimers. This behavior contrasts with that observed for the other plant lectins studied thus far, which form strong, obligate oligomers, indicating a distinctly different molecular basis for WGA function. For dimer formation, the four domains must be properly folded. Nevertheless, depending on the solution conditions, self-association may be coupled with folding of the labile domain. Therefore, dimerization may proceed as a rigid-body-like association or a folding-by-binding event. This hybrid behavior is not seen in other plant lectins. The emerging molecular picture for the WGA assembly highlights the need for a reexamination of existing ligand-binding data in the literature.

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Section: Unfolding Of Monomeric Wgasupporting

confidence: 76%

“…The fluorescence intensity of the monomer at pH 2 is seen to be significantly lower than that exhibited at higher pH values. In this regard, it is relevant to recall an early study on CNBr-treated WGA (25). In that study, a WGA form cleaved at Met 26 , i.e., near the middle of domain A, was obtained.…”

Section: Unfolding Of Monomeric Wgamentioning

confidence: 99%

Folding and Homodimerization of Wheat Germ Agglutinin

Portillo-Téllez

Bello

Salcedo

et al. 2011

Biophysical Journal

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“…If a carbohydrate is absent on the epithelium surface of some insects, the lectin will not be toxic. Thus, lectins showing insecticidal activity against the European corn borer are specific for Nacetylglucosamine and galactose/N-acetylgalactosamine residues, while lectins with binding specificity for mannose/glucose residues have no insecticidal effect (Czapla and Lang, 1990;Balasubramaniam et al, 1991). However, variability of sugar composition of glycosylated proteins does not seem to be important enough to explain the high specificity observed.…”

Section: Discussionmentioning

confidence: 97%

Modulation of a lectin insecticidal activity by carbohydrates

Triguéros

Wang

Père

et al. 2000

Arch. Insect Biochem. Physiol.

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Lectins from plants present an insecticidal activity most probably through their carbohydrate binding properties; as a consequence, their toxicity should vary with the presence of a competitive sugar in the ingested food. In order to test this hypothesis, we performed competition experiments between insecticidal activity and carbohydrate binding. For this purpose, we used a lectin from Lathyrus ochrus and the specific carbohydrate for this protein, glucose. In toxicological tests with Drosophila melanogaster, we observed a decrease of lectin toxicity when glucose was added to the larva-rearing medium. This result suggests that the toxicity of the lectin is correlated to its ability to bind sugar in the insect digestive tract and stresses the importance of sugar composition of the nutriment used for toxicological testing of lectins or in genetically modified plants.

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“…However, some evidence suggests that lectin toxicity is highly specific. Thus, lectins showing insecticidal activity against the European corn borer are specific for Nacetylglucosamine and galactose/N-acetylgalactosamine residues, while lectins with binding specificity for mannose/glucose residues have no insecticidal effect (Czapla and Lang, 1990;Balasubramaniam et al, 1991). For example, peanut lectin (from Arachis hypogaea) is toxic for the cowpea weevil larva (Murdock et al, 1990) and for the stem borer Chilo partellus Swinhoe (Law and Kfir, 1997), but any toxic effect was observed with the European corn borer, or with the Southern corn rootworm (Czapla and Lang, 1990).…”

Section: Discussionmentioning

confidence: 99%