NMR studies of protein surface accessibility

Characterization of protein surface accessibility represents a new frontier of structural biology. A surface accessibility investigation for two struc turally well-defined proteins, tendamistat and bovine pancreatic trypsin in hibitor, is performed here by a combined analysis of water-protein Overhaus er effects and paramagnetic perturbation profiles induced by the soluble sp in-label 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyI on NMR spectra. Th is approach seems to be reliable not only for distinguishing between buried and exposed residues but also for finding molecular locations where a netw ork of more ordered waters covers the protein surface. From the presented s et of data, an overall picture of the surface accessibility of the two prot eins can be inferred. Detailed knowledge of protein accessibility can form the basis for successful design of mutants with increased activity and/or g reater specificity.