Structural determinants stabilizing helical distortions related to proline

Area of Science:

• Structural biology
• Protein structure analysis

Background:

• Proline residues can introduce distortions in alpha-helices.
• Understanding these distortions is crucial for protein structure prediction and function.

Purpose of the Study:

• To comprehensively analyze and classify proline-induced distortions in alpha-helices.
• To identify recurring structural motifs accommodating these distortions.

Main Methods:

• Data mining of a non-redundant Protein Data Bank subset.
• Analysis of proline residues within contiguous helices and helix-linker-helix motifs.
• Classification based on linker length, proline position, and dihedral angles.

Main Results:

• Identified "typical" (65%) and "non-typical" (35%) proline distortions.
• Non-typical distortions often involve one or two linker residues, with proline at the second or third position of the second helix.
• Classified non-typical distortions into five canonical structures, including pi bulges and tight turns, accounting for 85% of cases.

Conclusions:

• A hierarchical classification system for proline-related helical distortions has been established.
• This classification reveals distinct structural determinants and hydrogen-bonding patterns for pi bulges and tight turns.
• The findings provide a robust framework for understanding proline's role in protein structure.