Deletion of a large domain in recombinant human procollagen II does not alter the thermal stability of the triple helix.

A construct of the human gene for procollagen II (COL2A1) was prepared with an internal deletion of 5 kilobases that removed 12 exons coding for 291 amino acids from near the NH2 terminus of the triple helix. The construct was then used to transfect stably a human tumor cell line (HT-1080), and clones secreting internally deleted pro alpha 1(II) chain of procollagen II were isolated. The protein was purified, and the thermal stability of the triple-helical domain was assayed by brief protease digestion. The thermal stability of the internally deleted protein was the same as that of intact collagen II even though the triple helix was 39% shorter. Additionally, the thermal stability of the collagenase A fragment was the same as that of the collagenase A fragment of normal collagen II even though it was 38% shorter. Analysis of the results suggested that the thermal stabilities of large fragments of collagen II depended primarily on their contents of -Gly-Pro-Hyp-triplets corrected for length.