Collagen molecule

Figure 14.1 Each polypeptide chain in the collagen molecule folds into an extended polyproline type II helix with a rise per turn along the helix of 9.6 A comprising 3.3 residues. In the collagen molecule three such chains are supercoiled about a common axis to form a 3000-A-long rod-like molecule. The amino acid sequence contains repeats of -Gly-X-Y- where X is often proline and Y is often hydroxyproline. (a) Ball and stick model of two turns of one polypeptide chain.

Figure 14.2 Models of a collagen-like peptide with a mutation Gly to Ala in the middle of the peptide (orange). Each polypeptide chain is folded into a polyproline type II helix and three chains form a superhelix similar to part of the collagen molecule. The alanine side chain is accommodated inside the superhelix causing a slight change in the twist of the individual chains, (a) Space-filling model, (b) Ribbon diagram. Compare with Figure 14.1c for the change caused by the alanine substitution. (Adapted from J. Bella et al.. Science 266 75-81, 1994.)...

The protein collagen undergoes hydrolytic degradation to gelatin in a manner which indicates the presence of a small minority of comparatively easily hydrolyzable bonds. Scatchard, Oncley, Williams, and Brown concluded that these are regularly spaced at intervals of about 1200 units in the collagen molecule. 

Weiner, S., Z. Kustanovich, E. Gil-Av, and W. Traub (1980), Dead Sea scroll parchments Unfolding of the collagen molecules and racemization of aspartic acid, Nature 287, 820-823. 

Miles, C.A. and Bailey, A.J. (2001) Thermally labile domains in the collagen molecules. Micron, 32, 325-332. 

Pakkanen, O., Hamalainen, E. R., Kivirikko, K. I., and Myllyharju.J. (2003). Assembly of stable human type I and III collagen molecules from hydroxylated recombinant chains in the yeast Pichia pastoris. Effect of an engineered C-terminal oligomerization domain foldon./. Biol. Chem. 278, 32478-32483. 

Figure 19.11 After cleavage of the terminal ends, the collagen molecule begins to assemble into a fibril via enzymatic cross-links. (From Nyman et al., 2005. Copyright 2003, with permission from Elsevier.)...

Type I collagen molecules are heterotrimeric molecules with an a chain composition of two al (I) chains and one o 2(I) chain from the COLlAl and COLl A2 genes, respectively. This a chain composition is written as [a 1(1)] 20 2 (I). A type I collagen molecule is synthesized as a procollagen type I molecule. The N- and C-terminal propeptides are cleaved as part of the processing in tissues and are called N- and C-propeptides, respectively. The human pro-o (I) and pro-o 2(I) have 246 and 247 residues in their C-propeptides, respectively. The C-propeptide contains interchain disulfide bonds, which are important for the stabilization of the three a chains in the endoplasmic reticulum (ER). 

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