Collagen amino acid content

The amino acids proline and hydroxyproline exert a stabilizing influence on the triple helix as described in detail in Sect. 4.5. By examining the CB peptides of collagen, a structural stability which is directly proportional to the itnino acid content may thus be found. It has, however, not been possible to synthesize model peptides displaying structural stability comparable to that of the native peptides having corresponding amino acid contents. 

Figure 9.2. Amino acid content (mol %) in collagen extract (dark columns) and serum proteins (light columns) from a skeleton from coastal Peru. Due to a prevalence of degraded and soluble collagen, the nonmineral-bound protein fraction shows a collagen amino acid profile.

The other example presented of a non-scrambled distribution of isotopes involves the synthesis of collagen. For a mature animal at steady state, we might expect extensive atomic scrambling in the sense that most of the non-essential amino acid content of this protein (78% of its carbon atoms) can be synthesized from the general pool of glycogenic substrates that arise from metabolism of all sugars and fats, although the pathway from fats is restricted... 

Excellent summaries have been prepared concerning the results of past attempts to arrive at the amino-acid contents of collagens and the gelatins derived therefrom (31, 38). Table III collects together the information suitable for a comparison of the class members of predominant present interest. It is desired to consider to what extent the chemical data parallel the results of the physical comparisons of the collagens. 

FIGURE 10.16 Structures of fibrous proteins, (a) Three-stranded supercoil of collagen, (b) three-strand supercoil of oc-keratin (wool and hair), (c) two strand supercoil of myosin (muscle). Each strand of a-keratin and myosin is a right handed helix. The two three stranded supercoils have different amino acid contents and periodicities, and arrange themselves into different fibrous sub-structures which are not shown. 

The amino acid sequence of the collagen type I (bone, skin, tendon) is nearly completely known6. The sequence of the different tripeptides in the archain shows a more or less statistic distribution. The content of the tripeptides in the archain of type I collagen, however, is quite different (Table 1). 

Hayashi, T., Nagai, Y. (1980). The anomalous behavior of collagen peptides on sodium dodecyl sulfate-polyacrylamide gel electrophoresis is due to the low content of hydrophobic amino acid residues. J. Biochem. (Tokyo) 87, 803-808. 

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