Protein Science, Vol 3, Issue 9 1570-1581, Copyright © 1994 by Cold Spring Harbor Laboratory Press

ARTICLE

Pseudodihedrals: Simplified protein backbone representation with knowledge-based energy

R. S. DEWITTE and E. I. SHAKHNOVICH
Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138

Pairwise contact energies do not explicitly take protein secondary structure into account, and so provide an incomplete description of conformational energy. In order to construct a Hamiltonian that specifically relates to protein backbone conformations, a simplified backbone angle is used. The pseudodihedral angle (the torsion angle between planes defined by 4 consecutive {alpha}-carbon atoms) provides a simplified backbone representation and continues to manifest information about secondary-structure elements: the pseudo-Ramachandran plot contains helical and sheetlike regions. The distribution of pseudodihedral angles is highly sensitive to the identity of the central pair of amino acids. Therefore, a sequence-dependent, knowledge-based potential energy was found according to a quasichemical approximation. These functions form complementary additions to the contact potentials currently in use. This pseudodihedral potential greatly enhances the ability to design sequences that are specific to a given conformation and also improves the ability to discriminate a native conformation from many other conformations.
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