464 R. KHESIN 



enzymes forming part of cytoplasmic structures. But it is known that certain 

 enzymes found in cytoplasm (e.g. catalase, according to Brächet) can also be 

 formed after the nuclei are removed. At the present very few data are available 

 concerning protein synthesis in the nuclei. Allfrey & Mirsky were the first to 

 show that during incubation of isolated thymus nuclei in certain conditions 

 there occurs incorporation of amino acids into proteins but these data are not 

 conclusive, for the incorporation of amino acids does not prove the de novo 

 synthesis of protein molecules. 



Our preHminary experiments have shown that, during incubation of isolated 

 nuclei, proteins are synthesized from amino acids approximately in the same 

 conditions in which proteins are formed during incubation of cytoplasmic 

 granules. The nature of the proteins synthesized by nuclei is still unknown. 



Summing up all stated above we can state that protein synthesis is effected 

 in the cell in certain cytoplasmic structures of the ergastoplasm and, perhaps, in 

 the nuclei, but conditions for the synthesis are created by different cell compo- 

 nents. Moreover, the very character of the structures involved in the synthesis 

 of proteins depends on other parts of the cell, especially on the cell nucleus. 



It is well known that all hving structures capable of synthesizing proteins 

 contain, in addition to protein, nucleic acid of some type. In this respect the 

 'light large granules' of the cytoplasm are not an exception. As mentioned above, 

 they contain ribonucleic acid. Beside this they contain a considerable quantity 

 of lipids. In general these structures represent comparatively highly-organized 

 formations, possessing, for example, a membrane and correspondingly endowed 

 with osmotic activity. They contain some enzymes, such as cathepsin, ribonu- 

 clease, phosphatase and others. In this cormection the question arises as to the 

 nature of the chemical components of cytoplasmic granviles which are directly 

 required for protein synthesis. This question involves another one: is protein 

 synthesis possible after destruction not only of the cells, but also of the intra- 

 cellular granules ? 



In order to answer these questions, experiments were undertaken in which 

 the 'light large granules' of the regenerating rat liver were destroyed by treat- 

 ment with acetone or ethanol. The preparations obtained from the granules 

 after removal of Upids consisted practically of two components — protein and 

 ribonucleic acid. It was found that during incubation of such preparations in 

 the presence of amino acids and the medium produced by mitochondria there 

 takes place a formation of protein, the amount of which, within 30 minutes of 

 incubation, is increased by 5-10%. Thus, the destruction of granules does not 

 deprive them of the capacity to synthesize proteins. Synthesis of some quantity 

 of protein, at least, may be effected in systems consisting of protein and nucleic 

 acid, provided that amino acids and certain cofactors are made available. 



Our preparations cannot be defined as individual nucleoproteins, but the 

 experimental results suggest the possibihty of protein synthesis in isolated 

 nucleoproteins. 



The data obtained show that protein synthesis requires a system devoid of 

 morphological structure, and only possessing chemical structures which consist 

 of protein and nucleic acid. It seems that in adequate conditions nucleoproteins 



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