MECHANISMS OF GENE ACTION 



285 



FIGURE 10.5. The a-helix con- 

 figuration of a protein. The a- 

 helix is held together by hydrogen 

 bonds between the amide group of 

 one amino acid and the carboxyl 

 oxygen of the amino acid located 

 three residues from it along the 

 polypeptide chain. Formed in this 

 way, the configuration is packed 

 very firmly, and there is no open 

 space in the center. The a-helix 

 is a very general structure which 

 will accommodate any amino acid 

 side chains. Proline causes a bend 

 in the chain (from Corey and Paul- 

 ing, 1955, Rend. Ist. Lombard Sci., 

 89:10). 



^ ^Vf 





ture. This feat ha.s already been achieved with a few small proteins in- 

 cluding adrenocorticotropic hormone (AC^TH) (39 amino acids), insulin 

 (51 amino acids), and ribonuclease (124 amino acids). The same meth- 

 ods can in principle be applied to all proteins, but, of course, the 



