Strain in protein structures as viewed through nonrotameric side chains: II. effects upon ligand binding

Area of Science:

• Biochemistry
• Structural Biology
• Protein Science

Background:

• Understanding protein-ligand interactions is crucial for drug discovery and enzyme engineering.
• The conformational flexibility of amino acid residues plays a significant role in protein function.
• Nonrotameric conformations, deviating from typical side-chain arrangements, are observed in proteins.

Purpose of the Study:

• To investigate the spatial relationship between nonrotameric amino acid residues and ligands in protein structures.
• To determine if ligand binding induces nonrotameric conformations in proteins.
• To explore the functional implications of nonrotamericity in protein-ligand complexes.

Main Methods:

• Analysis of 112 high-resolution (
• Identification and spatial mapping of nonrotameric residues relative to bound ligands.
• Comparison of protein-ligand complexes with their corresponding apo structures.

Main Results:

• Nonrotameric residues and their clusters are preferentially located in ligand- and substrate-binding sites.
• Specific residues like Asp, Glu, His, Met, and Asn are frequently nonrotameric near ligands.
• Ligand binding appears to induce nonrotamericity and strain in protein structures.
• The energetic cost of induced strain is not offset by increased hydrogen bonding or salt bridges.

Conclusions:

• Ligand binding induces strain via nonrotameric residue conformations, which may enhance enzymatic activity.
• The increased internal energy associated with nonrotamericity could facilitate product formation and release.
• These findings have potential applications in protein engineering for modifying enzyme activity.