Atomic environments of arginine side chains in proteins

Area of Science:

• Structural biology
• Computational biophysics
• Protein structure analysis

Background:

• Arginine residues play crucial roles in protein structure and function.
• Understanding the atomic environments surrounding arginine is essential for predicting protein behavior.
• Previous studies have explored amino acid interactions, but detailed geometric analysis of arginine packing is limited.

Purpose of the Study:

• To statistically analyze the atomic environments of arginine side chains in high-resolution protein structures.
• To identify and quantify the factors governing the packing of arginine residues.
• To provide insights into the geometric preferences of atom contacts around arginine.

Main Methods:

• Statistical analysis of 62 high-resolution protein structures.
• Classification of protein data into 19 atom types based on F.M. Richards' definition.
• Calculation of propensities for atom contacts with arginine side chains.
• Detailed geometric analysis of interacting atom pairs, including contact separation (R) and spatial distribution (theta, phi angles).

Main Results:

• Identified propensities for various atom types to interact with arginine side chains.
• Characterized the detailed geometry of these interactions, including distances and angular distributions.
• Compared geometrical distributions to reveal factors important for packing.
• Found that polarity, covalent constraints, volume occlusion, and solvent accessibility are key determinants of arginine side chain packing.

Conclusions:

• The packing of arginine side chains is primarily governed by a combination of physical and chemical factors.
• Understanding these determinants can aid in protein design and engineering.
• This analysis provides a quantitative framework for the structural context of arginine residues in proteins.