Hyperstable, Minimal-Length, and Blunt-Ended Collagen Heterotrimers

Most natural collagens are heterotrimers-triple helices formed from three non-identical peptide strands. The design of synthetic heterotrimeric collagen is challenging since a mixture of three different peptides can form as many as 27 unique triple helices. Here, we present a general method for the assembly of collagen heterotrimers with a wide range of lengths, thermal stabilities, and strand arrangements driven by complementary interstrand salt bridges between (2S,4S)-4-aminoproline and aspartate residues. We show how kinetic trapping of undesired trimers can be overcome by adjusting the annealing conditions to obtain the target heterotrimeric helix selectively under thermodynamic control. The design rules and annealing methods allowed the creation of the most stable supramolecular heterotrimer (32 residues, T_m = 76 °C) and the shortest stable heterotrimer (17 residues, T_m = 19 °C) to date. Furthermore, frame-shifting enabled, for the first time, the creation of a collagen triple helix with blunt ends.