Assignment of PolyProline II conformation and analysis of sequence--structure relationship

Area of Science:

• Structural biology
• Bioinformatics
• Biochemistry

Background:

• Proteins feature repetitive secondary structures like alpha-helices and beta-sheets.
• PolyProline II (PPII) helices, though less common, are increasingly recognized for their role in protein-protein interactions.

Purpose of the Study:

• To develop a reliable method for assigning PolyProline II (PPII) helix structures.
• To address limitations of current secondary structure assignment methods (SSAMs) in identifying PPII.

Main Methods:

• A consensus strategy was employed, comparing three SSAMs capable of PPII assignment.
• A new PPII assignment rule was defined within the DSSP framework, focusing on maximum coverage and minimal constraints.
• Only PPII helices of at least two residues were considered.

Main Results:

• The developed method assigns 5% of all amino acids to the PPII conformation.
• Sequence-structure relationships and amino acid preferences in PPII regions were analyzed.
• Distinct solvent accessibility and contact patterns were observed for PPII regions.

Conclusions:

• The proposed PPII assignment method integrates seamlessly with DSSP.
• This facilitates further analysis of PPII structures and their roles in protein function.
• The findings highlight the significance of PPII in protein architecture.