The structural ground underlying the pH-dependency of the dimer–tetramer transition of Diocleinae lectins was investigated by equilibrium sedimentation and X-ray crystal structure determination of wild-type and site-directed mutants of recombinant lectins. Synthetic genes coding for the full-length α-chains of the seed lectins of Dioclea guianensis (termed r-αDguia) and Dioclea grandiflora (termed r-αDGL) were designed and expressed in Escherichia coli. This pioneering approach, which will be described in detail in the present paper, yielded recombinant lectins displaying carbohydrate-binding activity, dimer–tetramer equilibria and crystal structures indistinguishable from their natural homologues. Conversion of the pH-stable tetrameric r-αDGL into a structure exhibiting pH-dependent dimer–tetramer transition was accomplished through mutations that abolished the interdimeric interactions at the central cavity of the tetrameric lectins. Both the central and the peripheral interacting regions bear structural information for formation of the canonical legume lectin tetramer. We hypothesize that the strength of the ionic contacts at these sites may be modulated by the pH, leading to dissociation of those lectin structures that are not locked into a pH-stable tetramer through interdimeric contacts networking the central cavity loops.
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Research Article|
December 21 2007
Insights into the structural basis of the pH-dependent dimer–tetramer equilibrium through crystallographic analysis of recombinant Diocleinae lectins
Celso S. Nagano;
Celso S. Nagano
*Instituto de Biomedicina de Valencia, C.S.I.C., Jaime Roig 11, 46010 Valencia, Spain
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Juan J. Calvete;
Juan J. Calvete
1
*Instituto de Biomedicina de Valencia, C.S.I.C., Jaime Roig 11, 46010 Valencia, Spain
1Correspondence can be addressed to either J. J. Calvete (email jcalvete@ibv.csic.es) for issues concerning X-ray crystallography or L. Sanz (email Libia.Sanz@ibv.csic.es) for issues related to molecular biology.
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Domingo Barettino;
Domingo Barettino
*Instituto de Biomedicina de Valencia, C.S.I.C., Jaime Roig 11, 46010 Valencia, Spain
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Alicia Pérez;
Alicia Pérez
*Instituto de Biomedicina de Valencia, C.S.I.C., Jaime Roig 11, 46010 Valencia, Spain
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Benildo S. Cavada;
Benildo S. Cavada
†BioMol-Lab, Departamento de Bioquímica e Biologia Molecular, Universidade Federal do Ceará, Fortaleza, CE 60451-970, Brazil
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Libia Sanz
Libia Sanz
1
*Instituto de Biomedicina de Valencia, C.S.I.C., Jaime Roig 11, 46010 Valencia, Spain
1Correspondence can be addressed to either J. J. Calvete (email jcalvete@ibv.csic.es) for issues concerning X-ray crystallography or L. Sanz (email Libia.Sanz@ibv.csic.es) for issues related to molecular biology.
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Publisher: Portland Press Ltd
Received:
July 17 2007
Revision Received:
September 25 2007
Accepted:
October 16 2007
Accepted Manuscript online:
October 16 2007
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© The Authors Journal compilation © 2008 Biochemical Society
2008
Biochem J (2008) 409 (2): 417–428.
Article history
Received:
July 17 2007
Revision Received:
September 25 2007
Accepted:
October 16 2007
Accepted Manuscript online:
October 16 2007
Citation
Celso S. Nagano, Juan J. Calvete, Domingo Barettino, Alicia Pérez, Benildo S. Cavada, Libia Sanz; Insights into the structural basis of the pH-dependent dimer–tetramer equilibrium through crystallographic analysis of recombinant Diocleinae lectins. Biochem J 15 January 2008; 409 (2): 417–428. doi: https://doi.org/10.1042/BJ20070942
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