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Geometry of interplanar residue contacts in protein structures
1Department of Mathematics, Stanford University, CA 94305-2125.
Summary
Protein side chains with aromatic or histidine rings show nonrandom spatial arrangements, favoring edge-to-edge or edge-to-center interactions over complete stacking. This impacts protein structure and function.
Area of Science:
- Structural biology
- Biochemistry
- Protein science
Background:
- Protein side chains contain planar groups like aromatic, guanidinium, amide, carboxyl, and imidazole.
- The spatial arrangement of these groups influences protein structure, stability, and function.
- Understanding these interactions is key to protein engineering and drug design.
Purpose of the Study:
- To analyze the relative spatial disposition of interacting side-chain planar groups in protein structures.
- To determine if these arrangements are random or follow specific geometric preferences.
- To investigate the role of electrostatic forces in mediating these interactions.
Main Methods:
- Analysis of 186 non-homologous, well-resolved protein structures.
- Geometric analysis of dihedral angles between various planar side-chain groups.
- Statistical evaluation of spatial distributions.
Main Results:
- Amide and carboxyl group interactions showed random dihedral angle distributions.
- Aromatic ring and histidine ring interactions exhibited significantly nonrandom, uniform dihedral angle distributions.
- Edge-to-edge and edge-to-center arrangements were prevalent, while complete stacking was uncommon.
Conclusions:
- Specific side-chain planar groups, particularly aromatic and histidine, exhibit nonrandom spatial preferences in proteins.
- These preferences suggest underlying geometric constraints or forces, potentially electrostatic, guiding their interactions.
- The findings provide insights into protein folding and the design of novel protein structures.