13 



The structure of ribonuclease in relation to its 

 enzymatic activity and physical properties* 



C.B. ANFINSEN 



Laboratory of Cellular Physiology and Metabolism, 

 National Heart Institute, Bethesda, Maryland 



In order to appreciate the present state of protein chemistry we need only 

 consider the material being covered in this symposium from the standpoint 

 of our position ten years ago. Although there was available at that time a 

 large amount of physical data relating to the behavior of proteins in solu- 

 tion and in the solid state, a rational interpretation of these data was essen- 

 tially impossible because of the almost complete absence of quantitative 

 information on the sequential structure of these molecules. Today, the 

 determination of the amino acid sequence of polypeptide chains has, in 

 general, become a technical problem of only moderate difficulty and the 

 application of available degradative methods is likely to permit the eluci- 

 dation of the covalent structure of almost any chosen protein whose mole- 

 cular weight lies within reasonable limits. 



Drs Hirs, Moore and Stein have presented to you a summary of their 

 precise studies on the structure of ribonuclease (see p. 211). Detailed refer- 

 ence to their original papers has not been made in the bibliography below 

 but can be found elsewhere in this volume. As they have pointed out, we 

 have also been belabouring this protein in Bethesda and have reached con- 

 clusions about the sequence of the molecule which are in good agreement 

 with their findings. In view of this agreement I will only discuss some of 

 the pertinent results which begin to enable us to correlate the activity and 

 physical behavior of this enzyme with its covalent and non-covalent structure. 



Before beginning these considerations I would like to refer briefly to two 

 methodological developments which may be of interest to this audience. 

 These methods have to do with the general problem of the specific hydro- 

 lysis of a protein molecule to yield reproducible fragments of moderate size, 

 a problem which we all recognize as fundamental in structural analysis. 



* Those recent studies discussed in this chapter, which were carried out at Bethesda, 

 are the combined efforts of Drs Michael Sela, W. F. Harrington, F. W. White, and 

 myself. I would like to emphasize my role as spokesman for this group. 



