Decoding elegant interplay among different stereo-electronic effects due to the ancient prolyl-4-hydroxylation...

Area of Science:

• Biochemistry
• Structural Biology
• Computational Chemistry

Background:

• Prolyl-4-hydroxylation is a vital post-translational modification (PTM) essential for collagen structure and function in multicellular organisms.
• The precise stereoelectronic mechanisms by which hydroxylation influences collagen's triple helix stability are not fully understood.
• Collagen stability relies on intricate interactions including ring pucker, torsional angles, peptide bond isomerization, and charge-transfer phenomena.

Purpose of the Study:

• To elucidate the correlation between prolyl-4-hydroxylation and collagen's structural stability.
• To analyze the stereo-electronic effects induced by 4(R)-hydroxylation in a collagenous peptide model.
• To quantify the impact of hydroxylation on key interactions governing helical stability.

Main Methods:

• Utilized density functional theory (DFT) calculations.
• Calibrated DFT methods against gold-standard ab initio computational techniques.
• Analyzed a physiologically relevant collagenous peptide: proline-4-hydroxyproline-glycine (PO4G).

Main Results:

• 4(R)-hydroxylation promotes an 'exo' pyrrolidine ring pucker.
• This hydroxylation optimizes main-chain torsional angles for a stable 'trans' peptide bond.
• Hydroxylation significantly enhances n→π* (0.9 kcal/mol) and σ→σ* charge-transfer interactions within the peptide.

Conclusions:

• Prolyl-4-hydroxylation critically influences collagen structure through specific stereo-electronic effects.
• The study reveals how hydroxylation optimizes ring pucker and charge-transfer interactions to ensure helical stability.
• These findings provide a deeper understanding of the molecular basis of collagen's structural integrity.