Stabilization mechanism of triple helical structure of collagen molecules

Abstract

The role of 4-hydroxyproline (Hyp) in stabilizing collagen triple helical structure has been investigated comprehensively. Recently it was emphasized that the preferential pyrrolidine ring pucker influenced by the stereoelectronic effects of substituted groups mainly affects the thermal stability of the triple helix. To examine this explanation, we synthesized and characterized (fPro R -Pro-Gly)10 and (fPro S -Pro-Gly)10. According to the results of CD and analytical ultracentrifugation, (fPro S -Pro-Gly)10 takes a triple helical structure and (fPro R -Pro-Gly)10 exists in a single chain structure, the trend of which is not consistent with the relationship between (Hyp S -Pro-Gly)10 and (Hyp R -Pro-Gly)10. In order to rationalize experimental results as a whole, we carried out DSC analyses and determined the thermodynamic parameters associated with the structural transition of these collagen model peptides. In this paper, we reported the DSC results for (Pro-Pro-Gly)10, (Pro-Hyp R -Gly)10 and (Pro-fPro R -Gly)10 as a part of this study. Based on those parameters, we concluded that Hyp and fPro stabilize the triple helix in different stabilizing mechanisms; the increased stability of (Pro-Hyp R -Gly)10 is ascribed primarily to the enthalpic effects while that of (Pro-fPro R -Gly)10 is achieved through the entropic ones.