462 R. KHESIN 



The conclusion was drawn from the above-mentioned facts that proteins can 

 be synthesized in certain conditions even after destruction of the cell. Integrity 

 of cell structure is not absolutely necessary for protein synthesis, which can 

 also take place in isolated structural components of cells. 



Later, in 1953-54, this conclusion was supported by the beautiful experiments 

 of Gale & Folkcs with partially destroyed staphylococci, by the studies of Straub 

 on amylase and penicillinase, the investigations of Sisakyan and of other scientists. 

 Now it is established beyond doubt that proteins may be formed not only in 

 intact cells but also in particular types of isolated cytoplasmic granules. The 

 question therefore arises concerning the character and mechanism of partici- 

 pation in this process of other structural components of the cell. 



Let us first consider the role played by the mitochondria. As already mentioned, 

 mitochondria form some substances which are required by other granules for 

 the synthesis of proteins. The nature of these substances has not yet been 

 elucidated. The active 'mitochondrial factor' is formed only in the course of 

 aerobic incubation of mitochondria; but in the presence of 'mitochondrial 

 factor' the cytoplasmic granules can synthesize proteins even in anaerobic 

 conditions. 



It has been found that the active factor is associated with a fraction obtained 

 from the incubation medium of mitochondria, which contains a large amount 

 of ribonucleic acid (up to 50% of dry weight of the active fraction). It is known 

 that mitochondria contain the major part of the oxidative enzymes of the cell 

 and partictilarly the cytochrome oxidase system. Hence, it appears that respira- 

 tion and protein synthesis are topographically separated in the cells ; respiration 

 is carried out mainly by mitochondria, while protein synthesis is effected by 

 other granules. 



It is also known that mitochondria together with hyaloplasm synthesize many 

 amino acids which are subsequently used for protein formation. Finally, mito- 

 chondria are the site of oxidative phosphorylation, which results in the synthesis 

 of the universal energy source, ATP. ATP is required for elaboration of the 

 'mitochondrial factor', and we may assimie that synthesis of proteins is associated 

 with utilization of the energy enclosed in the 'factor'. As a result of glycolysis, 

 ATP is also formed in hyaloplasm. 



A comparison of biochemical evidence with cytological data, obtained with the 

 aid of electron microscope by other authors, indicates that the 'light large 

 granules' are derived from the ergastoplasm. Therefore, the latter can be con- 

 sidered as the main site of protein synthesis in the cell. The other structural 

 parts of the cell in the first place, mitochondria and hyaloplasm, are involved 

 in making available the conditions required by crgastoplasmic structures for 

 protein synthesis. This in our opinion is the principal role played by these 

 elements of the cell where proteins are not directly synthesized, or are synthe- 

 sized on a small scale. 



Up till now we have left aside the role played by the cell nucleus ; as a matter 

 of fact, the important significance of this component is beyond any doubt. 



It is well known that formation in a cell of a variety of active enzymes — proteins 

 — depends on the properties of nuclear constituents. Indeed, it has been shown 



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