Tuning of collagen triple-helix stability in recombinant telechelic polymers.

The melting properties of various triblock copolymers with random coil middle blocks (100-800 amino acids) and triple helix-forming (Pro-Gly-Pro)(n) end blocks (n = 6-16) were compared. These gelatin-like molecules were produced as secreted proteins by recombinant yeast. The investigated series shows that the melting temperature (T(m)) can be genetically engineered to specific values within a very wide range by varying the length of the end block. Elongation of the end blocks also increased the stability of the helices under mechanical stress. The length-dependent melting free energy and T(m) of the (Pro-Gly-Pro)(n) helix appear to be comparable for these telechelic polymers and for free (Pro-Gly-Pro)(n) peptides. Accordingly, the T(m) of the polymers appeared to be tunable independently of the nature of the investigated non-cross-linking middle blocks. The flexibility of design and the amounts in which these nonanimal biopolymers can be produced (g/L range) create many possibilities for eventual medical application.