Joshi Ashutosh, Basak Trayambak, Mondal Bhaskar
School of Biosciences and Bioengineering, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175075, India.
School of Chemical Sciences, Indian Institute of Technology Mandi, Mandi, Himachal Pradesh 175075, India.
iScience. 2025 Apr 10;28(5):112393. doi: 10.1016/j.isci.2025.112393. eCollection 2025 May 16.
Prolyl-4-hydroxylation is an ancient evolutionarily conserved post-translational modification (PTM) critical for both structural and regulatory functions in multicellular life forms. This PTM plays a pivotal role in stabilizing collagen's triple helix by influencing the puckering of the pyrrolidine ring. The elegant interplay between ring pucker, torsional angles, peptide bond isomerization, and charge-transfer interactions (O···C=O n→π∗ and σ→σ∗) attaining the helical stability remains underappreciated. Using density functional theory calibrated against gold standard methods, we analyzed a physiologically relevant collagenous peptide proline-4-hydroxyproline-glycine (POG) to establish the correlation between stereo-electronic effects due to prolyl-4-hydroxylation. Our results show that 4()-hydroxylation promotes an ring pucker, optimizing main-chain torsional angles for a stable peptide bond and maximizing the n→π∗ interaction ( = 0.9 kcal/mol) by tuning Bürgi-Dunitz trajectory, and maximizes σ→σ∗ interactions between axial C-H σ-electrons and C-OH∗ orbitals of the pyrrolidine ring. This study reveals the intricate stereo-electronic effects driving collagen's structural stability.
脯氨酰-4-羟基化是一种古老的、进化上保守的翻译后修饰（PTM），对多细胞生命形式的结构和调节功能都至关重要。这种PTM通过影响吡咯烷环的褶皱在稳定胶原蛋白的三螺旋结构中起关键作用。环褶皱、扭转角、肽键异构化和电荷转移相互作用（O···C=O n→π∗和σ→σ∗）之间实现螺旋稳定性的精妙相互作用仍未得到充分认识。我们使用针对金标准方法校准的密度泛函理论，分析了一种生理相关的胶原肽脯氨酸-4-羟脯氨酸-甘氨酸（POG），以建立脯氨酰-4-羟基化引起的立体电子效应之间的相关性。我们的结果表明，4（）-羟基化促进环褶皱，优化主链扭转角以形成稳定的肽键，并通过调整 Bürgi-Dunitz 轨迹使n→π∗相互作用最大化（ = 0.9 kcal/mol），并使吡咯烷环的轴向C-H σ电子与C-OH∗轨道之间的σ→σ∗相互作用最大化。这项研究揭示了驱动胶原蛋白结构稳定性的复杂立体电子效应。
