TRIMERIC ASSEMBLY OF COLLAGEN-XII - EFFECT OF DELETION OF THE C-TERMINAL PART OF THE MOLECULE

The fibril-associated-collagens-with-interrupted (FACITs) are devoid o f large C-propeptides like those involved in the trimeric assembly of the fibrillar collagens. Under these conditions, the C-terminal non tr iple-helical domain (NC1) and the adjacent triple-helical domain (COL 1) are likely to be responsible for the trimeric assembly of these col lagen molecules. Using a recombinant minigene of one of the FACITs, co llagen XII, we show that a deletion covering most of the NC1 domain, e xcept the first seven residues containing a cysteine and constituting the main part of the conserved junction between the COL 1 and NC1 doma ins, does not prevent the formation of trimeric disulfide-bonded assem bly of truncated ct chains. These results suggest that if the non trip le-helical NC1 domain is involved in the initial events governing the trimeric assembly, it must be through its amino acid residues particip ating in the junction. Our data confirm also the results obtained in a previous paper (Mazzorana et al.: J. Biol. Chem. 268: 3029 -3032, 199 3) showing that the formation of disulfide bonds is dependent on hydro xylation and suggesting that the folding of the triple helix (or a par t of it) precedes the formation of the disulfide bonds.