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Protein surface accessibility represents a dimension of structural biology which has not been discussed in details so far, in spite of its fundamental role in controlling the molecular recognition process. In the present report the surface accessibility of α-bungarotoxin, a small and well characterized protein, has been investigated by analyzing its interaction with solvent and paramagnetic molecules in an integrated way. The presence of strong hydration sites, identified by a combined analysis of MD simulation and NMR results, seems to prevent the access of Gd(III)DTPA-BMA to the protein surface. On the contrary, the limited hydration of the α-bungarotoxin active site favors frequent encounters between the paramagnetic probe and the protein in the latter region. All the data obtained here for α-bungarotoxin suggest that shape and stability of the solvation shell control its surface accessibility and, hence, intermolecular interactions in a way which could be common to many other proteins. © 2007 Elsevier Inc. All rights reserved.

The S1 and S2 subunits of the spike glycoprotein of the coronavirus which is responsible for the severe acute respiratory syndrome (SARS) have been modelled, even though the corresponding amino acid sequences were not suitable for tertiary structure predictions with conventional homology and/or threading procedures. An indirect search for a protein structure to be used as a template for 3D modelling has been performed on the basis of the genomic organisation similarity generally exhibited by coronaviruses. The crystal structure of Clostridium botulinum neurotoxin B appeared to be structurally adaptable to human and canine coronavirus spike protein sequences and it was successfully used to model the two subunits of SARS coronavirus spike glycoprotein. The overall shape and the surface hydrophobicity of the two subunits in the obtained models suggest the localisation of the most relevant regions for their activity.