The Spatial Distribution of Local Mobility in Folded Proteins

A quantitative approach is developed to the study of the spatial distribution of amino acid mobility in protein structures. This method, which is based on bioinformatic and signal processing tools, makes it possible to study very large databases of structures simultaneously, and to search for the existence of domains within proteins which are defined by mobility effects, rather than by static structural considerations. It is shown that mobility is distributed nonuniformly in a substantial subset of structures in a large database; that nonuniform mobility distribution does not select for fold class; and that differences in local mobility distribution are correlated with differences in total mobility. Analyzed in light of previous results, these findings suggest that the dynamics of proteins with nonuniform distributions of mobility may exhibit dynamics dominated by local modes, rather than large-scale motions. We suggest that spatial mobility distribution may be a significant driver of protein evolution. It is also speculated that mobility distribution may act as a control on the hydrodynamic environment of proteins in solution.