TY - JOUR
T1 - Folding and homodimerization of wheat germ agglutinin
AU - Portillo-Téllez, María Del Carmen
AU - Bello, Martiniano
AU - Salcedo, Guillermo
AU - Gutiérrez, Gabriel
AU - Gómez-Vidales, Virginia
AU - García-Hernández, Enrique
N1 - Funding Information:
M.C.P.-T. received fellowships from the Consejo Nacional de Ciencia y Tecnología and Dirección General de Asuntos del Personal Académico during her graduate studies in the Programa de Doctorado en Ciencias Biomédicas, UNAM. This work was supported in part by the Dirección General de Asuntos del Personal Académico, UNAM (PAPIIT, grant IN204609) and Consejo Nacional de Ciencia y Tecnología (grant 129239).
PY - 2011/9/21
Y1 - 2011/9/21
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=80053127359&partnerID=8YFLogxK
U2 - 10.1016/j.bpj.2011.07.037
DO - 10.1016/j.bpj.2011.07.037
M3 - Artículo
SN - 0006-3495
VL - 101
SP - 1423
EP - 1431
JO - Biophysical Journal
JF - Biophysical Journal
IS - 6
ER -