A recombinant homotrimer of type I procollagen that lacks the central two D-periods. The thermal stability of the triple helix is decreased by 2 to 4 degrees C.

A D-period cassette system was developed that can be used to synthesize a variety of recombinant homotrimers of type I procollagen. A construct lacking the central two D-periods of pro alpha 1(I) chains was assembled and expressed as a recombinant protein in the mammalian cell line. The recombinant protein was purified to homogeneity and the thermal stability of the triple helix assayed by rapid protease digestion. The results indicated that deletion of the central 468 amino acids from the major triple helix lowered the thermal stability of the protein by 2 to 4 degrees C. The results therefore begin to define regions of the molecule that vary in their contributions to helical stability.