498 SESSION V. DISCUSSION 



a collection of" amino acids and of the medium in which mitochondria had been incubated 

 (prepared by the method of Siekcvitz and Khcsin.) It must be mentioned here that, 

 notwithstanding what Siekevitz has said, this medium contains an appreciable amount 

 of protein precipitated by trichloroacetic acid. We estimated the synthesis of protein by 

 the increase in protein nitrogen and by an increase in the number of peptide bonds as 

 shown by the biuret method. 



The results showed that the synthesis of protein in the disrupted mitochondria proceeds 

 even more intensively than in intact ones and the increase may amount to i7-i9°o of 

 the original protein. It must be supposed that this occurs on account of the greater acces- 

 sibility of the active centres of synthesis to the added amino acids in the disrupted, as 

 opposed to the intact, mitochondria. Furthermore, the possibihty is not ruled out that 

 there may be activation of some enzymes in the course of disruption of the mitochondria. 



Thus it was shown that the structural integrity of the mitochondria is not essential if 

 they are to retain their synthetic ability under conditions in which activizing energetic 

 factors are present. 



An examination of photographs of the disrupted mitochondria taken with the electron 

 microscope shows that, as a result of lysis, the envelope of the mitochondrium was punc- 

 tured and the fundamental part contained within it escaped. The granularity of the con- 

 tents, however, remained unimpaired, while the envelope of the mitochondrium was 

 scarcely affected. All this indicates that the synthetic ability of the mitochondrium is 

 concentrated in one or other of its component parts. These parts, however, are con- 

 siderably larger and more complicated formations than molecules of nucleoprotein, and 

 only a further degradation of the granular structures will enable us to solve the problem 

 posed at the beginning of this paper. 



The observation of synthesis of protein in disrupted mitochondria raised the question 

 of the way in which the energetic requirements of the synthesis are satisfied. Experiments 

 with enzyme poisons were carried out with a view to solving this problem. It appeared 

 that sodium fluoride does not in the least hinder synthesis either by complete or by dis- 

 rupted mitochondria. This indicates that, under the conditions which we were using, 

 glycolytic processes do not play a direct part in protein synthesis. The addition of dinitro- 

 phenol markedly inhibited the synthesis by intact and disrupted mitochondria, which is 

 evidence for the participation of a process of oxidative phosphorylation in the biosynthesis 

 of protein. At the same time, it is well known that the system of oxidative phosphorylation 

 is destroyed during the disruption of the mitochondrium. One must therefore suppose 

 that the medium from incubated mitochondria, which was added as an activator, in some 

 way reconstructs the processes of oxidative phosphorylation in the disrupted granules, 

 while the addition of dinitrophenol, by inhibiting oxidative phosphorylation, leads to a 

 loss of the ability to synthesize protein. 



Thus, although our investigations show that structural integrity of the mitochondria 

 is not essential to their synthetic ability, nevertheless, this synthetic abihty is only manifest 

 on the addition of a medium in which intact mitochondria have been incubated. 



That is, in fact, it raises the new question, how far is the integrity of the mitochondrium 

 necessary, not for the actual process of protein synthesis, but for providing the energy 

 required for it ? According to our preliminary evidence, this integrity is, in fact, necessary 

 for the elaboration of the active medium made by incubation. 



In conclusion, it must be mentioned that our results, as well as the reports in the 

 literature concerning the synthesis of protein in disrupted microsomes and other material 

 would appear to contradict the evidence put forward in Acad. A. I. Oparin's paper. We 

 believe that this contradiction is only apparent. It is simply evidence for the multiple 

 organization of the chain of biochemical processes leading to the biosynthesis of protein. 



B. S. DiSKiNA (U.S.S.R.): 



Proteolytic Activity Assodated with Deoxyribonucleic Acid-chymotrypsin 



The formation of nucleoproteins is one of the stages of the evolutionary development 

 of living material, and a study of their biological role is essential to an understanding of 

 the biochemical and biophysical bases of life. 



