INTERACTION OF COLLAGEN MAC ROMOLEC U LES 49 



in solution, and a run with trypsin and collagen denatured according 

 to the methods described by Grassniann et al. (1956). Although the 

 pattern is complex, it can be seen that for both the native collagen 

 plus trypsin ( NC + T ) and denatured collagen plus trypsin 

 ( DC + T ) runs an acidic peptide fraction ( Fraction I ) , not present 

 in either of the control runs, was obtained. Figure 27 shows the 

 electropherogram for the run with denatured collagen plus trypsin, 

 together with the distribution of radioactivity and an indication of 

 the relative specific activities (cpm/mg) found for the various frac- 

 tions. The high specific activity found for Fraction I indicated that 

 this peptide fraction must be rich in tyrosine, and this conclusion 

 was borne out by two-dimensional paper chromatography of an acid 

 hydrolysate of Fraction I (Fig. 28). Inspection of the chromato- 

 gram shows, as would be expected, a preponderance of aspartic and 

 glutamic acids and very little of the basic amino acids among the 

 polar residues. Fraction I also contains some hydroxyproline and 

 a considerable amount of tyrosine, some of which is present in the 

 hydrolysate as the mono-iodo-compound, the latter spot being radio- 

 active. Unfortunately, the yield of Fraction I was too small to allow 

 further fractionation, but experiments are under way to accumulate 

 a sufficient quantity of this fraction for a thorough characterization 

 of the peptides. 



In summary, it can be said that the effect of proteases such as 

 trypsin and pepsin on the TC macromolecule appears to be a rela- 

 tively slight modification, probably in "end regions," which, while 

 leaving intact the helical configuration of the polypeptide chains 

 comprising the macromolecule, drastically modifies its end-to-end 

 polymerization properties. These changes in the "reactivity" of the 

 macromolecule are accompanied by the liberation of a peptide or 

 peptides relatively rich in tyrosine. The results to date are com- 

 pletely compatible with the "end-chain" mechanism for end-to-end 

 polymerization of TC and suggest that the small tyrosine content 

 of collagen may be importantly involved in the mechanism by which 

 such "end-chains" interact in orderly fashion during polymerization. 



References 



Bear, R, S. 1952. The structure of collagen fibrils. Advances in Protein Chem. 7: 



69:160. 

 Bear, R. S., and R. S. Morgan. 1957. The composition of bands and interbands of 



collagen. In R. E. Tunbridge (ed.). Connective Tissue. Blackwell Scientific 



Publications, Oxford. Pp. 321-333. 



