Atom depth analysis delineates mechanisms of protein intermolecular interactions

Area of Science:

• Structural biology
• Biochemistry
• Protein dynamics

Background:

• Understanding protein-protein interactions is crucial for deciphering biological processes.
• Non-random mechanisms drive protein association, but the underlying structural determinants are not fully understood.

Purpose of the Study:

• To systematically analyze amino acid distribution within protein structures.
• To identify how amino acid positioning relates to protein-protein interaction mechanisms.

Main Methods:

• Analysis of 2,410 resolved protein structures from the Protein Data Bank.
• Exclusion of structures with modified surfaces due to ligand interactions.
• Evaluation of 3D atom depth and amino acid population across seven defined structural layers.

Main Results:

• Proteins exhibit distinct amino acid distributions from core to surface.
• Hydrophilic and charged residues (Q, R, K, N, D) increase towards the surface.
• Hydrophobic residues (V, I, L, A, C, G) are more abundant in the protein core.
• Outer layers are enriched in glutamate (E) and lysine (K), forming specific electrodynamics maps.

Conclusions:

• Amino acid distribution in protein structures is non-random and layer-dependent.
• Surface-exposed charged residues (E, K) may act as 'protein signatures' for long-range interactions.
• These surface features likely facilitate the formation of encounter complexes and subsequent protein-protein interactions.