LOCAL INTERACTIONS AND PROTEIN-FOLDING - A 3-DIMENSIONAL OFF-LATTICE APPROACH

The thermodynamic behavior of a three-dimensional off-lattice model fo r protein folding is probed. The model has only two types of residues, hydrophobic and hydrophilic. In absence of local interactions, native structure formation does not occur for the temperatures considered. B y including sequence independent local interactions, which qualitative ly reproduce local properties of functional proteins, the dominance of a native state for many sequences is observed. As in lattice model ap proaches, folding takes place by gradual compactification, followed by a sequence dependent folding transition. Our results differ from latt ice approaches in that bimodal energy distributions are not observed a nd that high folding temperatures are accompanied by relatively low te mperatures for the peak of the specific heat. Also, in contrast to ear lier studies using lattice models, our results convincingly demonstrat e that one does not need more than two types of residues to generate s equences with good thermodynamic folding properties in three dimension s. (C) 1997 American Institute of Physics.