β‐Bend conformation of CH3CO‐Pro‐Pro‐Gly‐Pro‐NHCH3: Implications for posttranslational proline hydroxylation in collagen

Abstract Conformational‐energy computations have been carried out for the N ‐acetyl‐ N ′‐methylamides of the Pro‐Pro, Pro‐Gly, and Gly‐Pro dipeptides and of the Pro‐Pro‐Gly‐Pro tetrapeptide, serving as models for the conformational analysis of single‐stranded poly(Gly‐Pro‐Pro). The probability of β‐bend formation for the Pro‐Gly sequence is very high, viz., 0.72 for the terminally blocked Pro‐Gly dipeptide, and rises to 0.86 in the tetrapeptide. The β‐bend conformations of the Pro‐Gly sequence are of low energy in single‐chain poly(Gly‐Pro‐Pro) as well. The β‐bend structure had been postulated earlier to be a requirement for post‐translational proline hydroxylation during the biosynthesis of collagen. The present results lend strong support to this proposal by demonstrating that the β‐bend structure is energetically favorable and hence can be accommodated easily in single‐stranded poly(Gly‐Pro‐Pro).