Predicting Collagen Triple Helix Stability through Additive Effects of Terminal Residues and Caps

Abstract

Collagen model peptides (CMPs) consisting of proline-(2S,4R)-hydroxyproline-glycine (POG) repeats have provided a breadth of knowledge of the triple helical structure of collagen, the most abundant protein in mammals. Predictive tools for triple helix stability have, however, lagged behind since the effect of CMPs with different frames ([POG] n , [OGP] n , or [GPO] n ) and capped or uncapped termini have so far been underestimated. Here, we elucidated the impact of the frame, terminal functional group and its charge on the stability of collagen triple helices. Combined experimental and theoretical studies with frame-shifted, capped and uncapped CMPs revealed that electrostatic interactions, strand preorganization, interstrand H-bonding, and steric repulsion at the termini contribute to triple helix stability. We show that these individual contributions are additive and allow for the prediction of the melting temperatures of CMP trimers.

Consequences of incorporating thiaproline and its oxidized derivatives into collagen triple helices

“…The oxidized derivative CMPs are designated as X-Thp', Y-Thp', X-Thp", and Y-Thp". Since the electrostatic interactions induced by the terminal functional groups were shown to affect the triple helix stability (Chiu & Horng, 2021;Fiala et al, 2022Fiala et al, , 2023, we used fully capped CMPs (acetylated N-terminus and amidated C-terminus) as our peptide models to avoid such interactions. The sequences of the designed CMPs are shown in Table 1.…”

Electronic Control of Polyproline II Helix Stability via the Identity of Acyl Capping Groups: the Pivaloyl Group Particularly Promotes PPII

“…K trans/cis is commonly used as a readily quantified proxy for the strength of n →π* interactions, including analysis in organic solvents [19] . However, K trans/cis also is impacted by the steric effects of the acyl group [11a,12a,16,18f,20] . More broadly, K trans/cis does not address effects on, for example, the adoption of PPII versus α‐helix versus β conformation, that is, impacts on the inherent conformational preferences at an amino acid.…”