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The link between sequence and conformation in protein structures appears to be stereochemically established.
Vibin Ramakrishnan1, Ranjit Ranbhor, Anil Kumar
1School of Biosciences and Bioengineering, Indian Institute of Technology Bombay, Mumbai 400076, India.
The Journal of Physical Chemistry. B
|May 5, 2006
Summary
Altering peptide stereochemistry dramatically impacts its solvent sensitivity by changing electrostatic interactions. This finding explains differences in peptide properties and may reveal protein sensitivity to amino acid sequences.
Area of Science:
- Biophysics
- Computational Chemistry
- Protein Science
Background:
- Understanding the relationship between amino acid sequence and protein structure is crucial in molecular biology.
- Peptide conformation and properties are known to be influenced by stereochemistry, but the precise mechanisms are not fully understood.
- Differences in solvent sensitivity and physical properties between poly-L and alternating-L,D peptides have been observed but lacked a clear explanation.
Purpose of the Study:
- To investigate the effect of stereochemical mutation on peptide conformation and solvent sensitivity.
- To elucidate the molecular basis for differences in properties between poly-L and alternating-L,D peptide structures.
- To explore the role of peptide dipolar interactions and electrostatics in determining these properties.
Main Methods:
- Molecular dynamics analysis was employed to study end-protected octa-alanine (Ac-Ala8-NHMe).
- Simulations compared the poly-L structure with an alternating-L,D stereochemical structure.
- Atomistic details of molecular folds and interpeptide electrostatic interactions were examined.
Main Results:
- Stereochemical mutation from poly-L to alternating-L,D structure caused a significant shift from high to low solvent sensitivity.
- The two structures exhibit different relationships between local and nonlocal peptide dipolar interactions, either conflicting or harmonious.
- The transformation from conflicting to harmonious interpeptide electrostatics in the alternating-L,D structure explains observed differences in peptide properties like stiffness and solvent sensitivity.
Conclusions:
- Stereochemistry fundamentally dictates the nature of interpeptide electrostatics, governing peptide properties.
- The findings resolve the long-standing puzzle of differing properties between poly-L and alternating-L,D peptides.
- Poly-L stereochemistry may be key to protein sensitivity to side-chain structures and their desolvating effects on peptide electrostatics.