Unraveling the Asymmetric Hydration Dynamics and Water-Mediated Stabilization in Collagen Heterotrimers.
Collagen's triple helix structure is fundamental to the mechanical integrity of bodily tissues, and its stability is vital for optimal physiological function. While the stabilization mechanisms of simple, symmetric collagen homotrimers have been previously studied, the hydration dynamics of native-like collagen heterotrimers which comprise the vast majority of human collagens remain largely unexplored. In this study, we investigated the complex role of water in stabilizing heterotrimeric collagen model peptides (CMPs) using extensive molecular dynamics (MD) simulations. We examined structurally diverse AAB-type and ABC-type heterotrimers exhibiting varying experimental stability profiles to investigate how sequence asymmetry influences hydration organization and collagen stability. Our simulations revealed that water molecules dynamically organize around these complex structures, forming topological water networks (TWNs) via intermolecular hydrogen bonds. Quantitative analyses of peptide-water interactions, hydration-water dynamics, and normalized TWN counts, together with residue- and chain-resolved TWN characterization, demonstrated that hydration-shell organization is strongly sequence dependent and differs among heterotrimers with distinct thermal stabilities. In particular, the more thermally stable heterotrimers exhibited a greater propensity for hydration-shell water molecules to participate in cyclic TWNs, accompanied by reduced hydration-water mobility and favorable interchain hydrogen-bonding interactions. These findings extend our previous observations on collagen homotrimers and provide new atomistic insight into the sequence-dependent organization of hydration water surrounding collagen heterotrimers, suggesting that organized hydration water contributes to collagen stability in concert with interchain hydrogen bonding and hydration-water dynamics rather than acting as an independent stabilization mechanism.