Cell Structure and Protein Synthesis 



R. KHESIN 



Institute of Biophysics, Academy of Sciences of the U.S.S.R., Moscow 



In considering the problem of the origin of life, the most important question 

 is that of origination and reproduction (synthesis) of protein, for the process 

 of protein formation is, in fact, the basic process in vital activity of organisms 

 at all stages of their evolutionary development. As far as we know, at the con- 

 temporary stage of evolution synthesis of proteins in natural conditions takes 

 place only within cells. Indeed, organisms which are at the pre-cellular stage of 

 development, such as viruses and phages, are capable of reproducing their own 

 protein component only in the host's cells. Relatively recently, in 1946, Northrop 

 stressed the significance of the fact that three fundamental reactions of Uving 

 matter, synthesis of proteins, photosynthesis and fixation of nitrogen, all require 

 energy and all are hitherto inseparable from the activity of hving, intact cells. 

 Thus, the question arises, whether the whole cell structure in its integrity is 

 required for effecting synthesis of proteins, and what is the role of the various 

 cell components in different phases of this process. 



The first data on this question were obtained by Winnick et al., beginning 

 from 1948, when it was shown that labelled amino acids are, in certain conditions, 

 incorporated into the proteins when incubated with preparations obtained from 

 destroyed cells. However, the incorporation of amino acids apparently can take 

 place in experiments in vitro as a result of processes by no means identical with 

 synthesis of proteins. Therefore we cannot estimate protein synthesis merely 

 relying on the evidence of incorporation of amino acids in vitro. 



In 1952 we made an attempt to solve the problem of protein synthesis after 

 destruction of cells; for this purpose we studied the synthesis of an enzyme 

 amylase, during incubation of homogenates and isolated cytoplasmic granules 

 from pigeon's pancreas. In these experiments the tissue was ground and the 

 homogenates, freed from the remaining intact cells and from a considerable part 

 of the nuclei, were centrifuged in order to separate cytoplasmic granules. It was 

 found that during aerobic incubation of a suspension of these granules in a 

 medium containing salts, glucose, adenosine triphosphate (ATP), cytochrome 

 c, and a respiratory substrate, in the presence of a set of amino acids, there 

 takes place synthesis of amylase. It should be mentioned that amylase formation 

 required the simultaneous presence in the medium of all those amino acids 

 which form part of the enzyme protein. In the absence of even one of the amino 

 acids, amylase is not synthesized. It should be noted that in these experiments 

 only a small quantity of the enzyme was formed, amounting to a few per cent of 

 its initial content. 



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