Amino-terminal domain, collagen

Fig. 49.5. Type IV collagen contains a globular carboxy-terminal domain (A), which forms tropocollagen dimers (hexamers of collagen, B). Four dimers associate at the amino-terminal domains to form a 7S domain (C), and the tetramers form a lattice (D), which provides structural support to the basal lamina.

Dublet, B., Oh, S., Sugrue, S.P. et at. (1989). The structure of avian typeXII collagen- a-l(XII) chains contain 190 kDa non-triple helical amino-terminal domains and form homotrimeric molecules. ]. Biol. Chem., 264, 13150-6. 

Type XVII collagen is composed of three identical procollagen polypeptides, each about 1,500 amino acids in length. It has a tadpole-like shape under physiological conditions (deduced from rotary shadowing electron microscopy of bovine cell lines or the pure protein). The protein is one of very few proteins whose N- and C-termini are inverted with respect to the membrane. In nearly all transmembrane proteins, for example integrins, the C-terminus is cytosolic and the N-terminus is extracellular. In type XVII collagen, the cytosolic N-terminal domain comprises about a third of the amino acid residues... 

Dixit SN, Mainardi GL, Beachey EH, et al. 7S domain consti-mtes the amino-terminal end of type IV collagen An immunohistochemical smdy. Coll Rel Res. 1983 3 263-273. 

Pihlajamaa, T., Lankinen, H., Ylostalo, J., Valmu, L., Jaalinoja, J., Zaucke, F. Characterization of recombinant amino-terminal NC4 domain of human collagen IX—Interaction with glycosaminoglycans and cartilage oligomeric matrix protein. J. Biol. Chem. 2004, 279 (23), 24265-24273. 

At the amino acid level, type XXIII collagen is similar to type XIII and XXV collagens with 54 and 56% identity, respectively. There is high identity across the 20-amino-acid C-terminal NC domain. In addition, the... 

The amino acid sequence of decorin includes six cysteine residues paired to form three disulphides (23). The crystal structure of decorin (21) revealed that the four cysteines on the A -terminal side of the LRR domain contained within a CxjCxCx C motif form a cystine knot, with the first cysteine connected to the third and the second to the fourth. The third disulphide located toward the C-terminal end of the LRR domain connects LRRs 11 and 12, providing a stable scaffold anchoring the ends of the flexible ear loop. Collectively, these three disulphides, and the tertiary structure they maintain, are critical for function because chemical reduction (23) leads to irreversible loss of the ability of decorin to bind to collagen (see below). 

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