Pseudodihedrals: simplified protein backbone representation with knowledge-based energy

Area of Science:

• Structural biology
• Computational chemistry
• Biophysics

Background:

• Pairwise contact energies offer an incomplete description of protein conformational energy as they do not explicitly account for secondary structure.
• A simplified representation of protein backbone conformations is needed to improve energy calculations.

Purpose of the Study:

• To develop a more accurate method for describing protein backbone conformations and conformational energy.
• To enhance the ability to design protein sequences specific to a given conformation and to distinguish native conformations.

Main Methods:

• A simplified backbone angle, the pseudodihedral angle, was used to represent protein backbone conformations.
• The pseudo-Ramachandran plot was utilized to visualize secondary structure elements.
• A sequence-dependent, knowledge-based potential energy function was derived using a quasichemical approximation based on pseudodihedral angle distributions.

Main Results:

• The pseudodihedral angle effectively represents protein secondary structure elements, with distinct regions for helical and sheetlike conformations observed in the pseudo-Ramachandran plot.
• The distribution of pseudodihedral angles demonstrated high sensitivity to the identity of adjacent amino acid pairs.
• The developed sequence-dependent potential energy functions were found to complement existing contact potentials.

Conclusions:

• The pseudodihedral potential significantly improves the design of protein sequences tailored to specific conformations.
• This approach enhances the discrimination of native protein conformations from non-native ones.
• The pseudodihedral angle offers a valuable tool for understanding and predicting protein structure and function.