CHAPTER XIII 

 THE SUMMARY OF PART V 



1 



Protein having A-structure may be converted into B-structure 

 under the effect of ^'-factor, whereas the protein thus converted to have 

 ^-structure w^ill return to ^-structure under ^-factor. The writer 

 designates such a phenomenon as reversibility of protein structure, 

 and regards it as the "memory" of the former structure. This pheno- 

 menon appears to be common in usual proteins but especially manifest 

 in the protoplasm, and may be indicated as follows : 



6-factor 



^-structure .Z ^-structure, 



^-factor 



wherein both a- and &-f actor are various chemical or physical agents, 

 such as temperature, light, or hormones, yl-structure may be stable 

 under the effect of c-factor, and jB-structure under ^-factor. 



However, protein having 5-structure frequently fails to be conver- 

 ted into >l-structure by the mere change of the environmental factor. 

 In such a case, some "stimulus" is needed to induce the change, the 

 change being prompted by a disturbance in the protein structure in 

 duced by the "stimulus". This may be compared to the conversion 

 of supercooled water into ice by a certain "stimulus" like a mechanical 

 agitation. 



If unfolding and refolding of polypeptide chains are required for 

 the structural conversion of a protein, "stimulus" may favour the 

 unfolding, that will be followed by the refolding, which the latter is 

 specific to the factor or environment under which the protein is 

 placed. 



The change from A lo B structure and from B to A structure 

 appears to take place easily when the change is repeated ; in other 

 words, the repetition of the reversible change may result in the fa- 

 cility of the change, the memory being thus strengthened. 



The intensification of the memory is presumably raised by the 

 removal of structural factors which prevent the reversible change. 

 The removal of such preventing factors may be achieved the more 



