Collagen structural models

The detection of the collagen-like threefold symmetric polypeptides, polyglycine4 and polyproline5, was the first help to elucidate the collagen structure using a synthetic peptide model. 

Kilchherr, E., Hofmann, H., Steigemann, W., and Engel, J. (1985). Structural model of the collagen-like region of Clq comprising the kink region and the fibre-like packing of the six triple helices. / Mol. Biol. 186, 403-415. 

Furthmayr, H., Wiedemann, H., Timpl, R., Odermatt, E., and Engel,J (1983). Electron microscopical approach to a structural model of intima collagen. Biochem. J. 211, 303-311. 

Figure 2.20. Models of collagen structure. (A) Model of three parallel left-handed helixes of collagen showing the location of Coc (C) for chains A, B, and C. Note all glycines are found in C-l position because this is the only amino acid residue that can be accommodated at the center of the triple helix. Later studies by Ramachan-dran and co-workers indicated that the three chains are wrapped around each other (B) in a right-handed superhelix. The axial rise per residue is 0.29 nm, and the axial displacement of different Coc atoms is shown in parentheses in angstroms.

It should be pointed out that Schmitt, et al. (1942) have shown, under certain conditions in the electron microscope, that collagen fibrils can apparently extend manyfold. This led Bear (1952) to suggest that a successful model should allow for such extensibility. However, under all other conditions collagen fibers have proved essentially inextensible beyond about 10% over rest-length, and in recent years this requirement for the collagen structure seems to have been generally abandoned. 

The description of collagen structures I and II which follow are adopted in part from a lucid discussion of these models by Rich and Crick (1968). A complete account of these structures, including the details of the derivation of the final models and complete sets of atomic coordinates has recently been published (Rich and Crick, 1961). 

Next, we discuss the collagen, which takes the triple helix structure. The amino acid sequence of collagen fibril consists of the repeating amino-acid sequence unit [Gly-Xaa-Yaa]n, where Xaa and Yaa are frequently occupied by prolyl (Pro) and 4-hydroxyprolyl (Hyp) residues, respectively. It is well known that the sequential model polypeptides such as [Pro-Ala-Gly]n or [Pro-Pro-Gly]n take the triple-helix conformation similar to that of collagen, as studied by X-ray diffraction and C, N CP-MAS NMR. This section focuses on the structure of [Pro-Ala-Gly]n, and the collagen structure as described by H CRAMPS NMR. 

The three-dimensional organization of type 1 collagen molecules within a fibril has been the subject of extensive research over the past 40 years [Fraser et al., 1983 Katz and li, 1972,1973a, b, 1981 Miller, 1976 Ramachandran, 1967 Yamuchi et al, 1986]. Many structural models have been proposed based on... 

Early in our studies it was expected that the post-translational modification of proline hydroxylation, so important to proper collagen structure and function, would raise the value of the temperature, T, for the onset of the inverse temperature transition for models of elastin. Accordingly, hydroxyproline (Hyp) was incorporated by chemical synthesis into the basic repeating sequence to give the protein-based polymers poly[fvs,i(Val-Pro-Gly-Val-Gly), fHyp( al-Hyp-Gly-Val-Gly)], where f sl -i- fnyp = 1 and values of fnyp were 0, 0.01, and 0.1. The effect of prolyl hydroxylation is shown in Figure 7.49. Replacement of proline by hydroxyproline markedly raises the temperature for hydrophobic association. Prolyl hydroxylation moves the movable cusp of... 

In this work we perform a corrrputer modeling of water molecules with fragments of proteins corrtairringthe arrtino add sequence Gly Pro-Pro. These fragments are the parts of the core stmctural rrrrit of collagen, structured into supramolecular triple helix. 

FIGURE 2.1 Gly Pro-Pro triple helix as a model of collagen structure with 8 A water shell. View 1. 

Figure 5.9 Structure of a model for a triple helical collagen structure (PDB IBKV) [403],...

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