PMID: 23132862

Authors:

Boudko SP, Bachinger HP

Title:

The NC2 domain of type IX collagen determines the chain register of the triple helix.

Journal:

J Biol Chem. 2012 Nov 6.

Abstract:

Precise mapping and unraveling the mechanism of interaction or degradation of a certain type of collagen triple helix requires the generation of short and stable collagenous fragments. This is a great challenge especially for hetero-trimeric collagens, where chain composition and register (stagger) are important factors. No system has been reported that can be efficiently used to generate a natural collagenous fragment with exact chain composition and desired chain register. The NC2 domain (only 35-50 residues) of FACIT collagens is a potent trimerization domain. In case of type IX collagen it provides the efficient selection and hetero-trimerization of three distinct chains. The ability of the NC2 domain to determine the chain register of the triple helix is studied. We generated three possible sequence combinations (alpha1alpha1alpha2, alpha1alpha2alpha1, alpha2alpha1alpha1) of a type I collagen fragment (the binding region for the von Willebrand factor A3 domain) attached to the NC2 domain. In addition, two control combinations were produced that constitute homo-trimers of (alpha1)3 or (alpha2)3. For the hetero-trimeric constructs, alpha1alpha1alpha2 demonstrated a higher melting temperature than the other two. Binding experiments with the von Willebrand factor A3 domain revealed the homo-trimer of (alpha1)3 as the strongest binding construct, whereas the homo-trimer of (alpha2)3 showed no binding. For hetero-trimers, alpha1alpha1alpha2 was found to be the strongest binding construct. Differences in thermal stability and binding to the A3 domain unambiguously demonstrate that the NC2 domain of type IX collagen determines not only the chain composition but also the chain register of the adjacent triple helix.