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An Overview of Structural Studies of the Plant Lectin Protein Concanavalin A. Professor John R Helliwell, Chemistry Department, University of Manchester, M13 9PL, UK, Fax: 44-161-275-4686, Email: John.Helliwell@man.ac.uk

Development of crystallographic methods involving ultra-resolution, multi-wavelength anomalous scattering (now known as MAD) and Laue diffraction have been undertaken and applied in the protein crystallography study of the saccharide protein concanavalin A. Thus the structure of the protein has been determined with small molecule accuracy i.e. a data to parameter ratio free of any distorting influences of the restraints; this has been made possible using instrumentation at the CHESS multipole wiggler, cryo cooling of the crystal and a CCD detector. The use of MAD at the Mn K-edge involving 3 wavelengths at ELETTRA, Trieste has been used to determine the occupancy of the transition metal site in the as-extracted protein, which is known to `tolerate' impurity metal atoms, thus building on the approach used to study pea lectin involving two wavelengths undertaken at Daresbury 7.2 many years ago. The development of neutron Laue diffraction in recent years at ILL, Grenoble, synergistic on the SR Laue development, is allowing the H/D dynamics of concanavalin A to be studied. High resolution mannoside and glucoside concanavalin A crystal structures, based on Daresbury SRS 7.2, 9.6 and 9.5 data sets, have formed the basis for a very recent molecular dynamics study of concanavalin A embracing a 500 psec simulation using an SG Challenge and the `AMBER' package (version 4.1). Thus molecular recognition similarities and differences, especially in the kind of mobility of each sugar seen in the MD, have been explored and compared with the ADP's of the sugar atoms, as well as with literature calorimetric data. Concanavalin A has thus been both a vehicle for SR and neutron crystallographic methods development in the last 10 years as well as being a fascinating molecular structure in its own right, implicated in cell to cell cross-linking and, in its glucose recognition, with potentiality to serve as a novel glucose biosensor.

Acknowledgements

This work has been undertaken over the last 10 years with various colleagues and students.