140 



C. B. ANFINSEN AND R. R. REDFIELD 



• TETRAPEPTIDE 

 o ACTIVITY 



no 



HlOO^ 



O 



80 5 



60 = 



± 



40 



20 





5 10 15 20 25 ^ 



MINUTES OF DIGESTION 



Fig. 12. The appearance of the tetrapeptide, -asp.ala,ser.val, and the loss in 

 enzyme activity during the digestion of native ribonuclease with pepsin. 



the linear polypeptide sense but not in terms of the three-dimensional picture. 

 Whether the pepsin activation brings about changes not related to peptide bond 

 rupture, such as the so-called "denaturase" action suggested by Linderstrj^m- 

 Lang and his colleagues (1950), cannot be answered without further study. 



In conclusion, the question might be raised as to the biological significance of 

 the complex, highly restricted chain structure which accompanies what appears 

 to be a relatively more simple catalytic core. One may speculate whether urea- 

 insensitive, "simple" enzymes, such as ribonuclease might not represent a class 



Lys.Clu 



Val.Ser.AkAs 



Sul)t^^\SiT\ 



\ 



^Photool(lJ4tio^ 

 o( histi4ine 



Fig. 13. Schematic representation of points of attack of native ribonuclease by 

 various reagents. 



