Thialysine systems

THIALYSINE, THIAISOLEUGINE AND THIAPROLINE AS INHIBITORS IN PROTEIN SYNTHESIZING SYSTEMS... 

Recently we had the opportunity to test the activity of thialysine in protein synthesizing systems from either E.coli,rat liver and rabbit reticulocytes,in a study directed to investigate the activity of another lysine analog,selenalysine(22). It was first studied the activation of thialysine by E.coli and rat liver amino-acyl -tRNA synthetases,by assaying either the ATP-PPi... 

In the ATP-PPi exchange with both E.coli and rat liver synthetases the Km values obtained with thialysine as substrate were similar to those of lysine,as shown in Table I. On the contrary the V values for thialysine were in both systems around forty per cent of that of lysine. When lysine and thialysine were present together in 1 1 molar ratio,the obtained V value indicated that lysine and thialysine are activated by the same enzyme. 

Further the effects of thialysine on lysine or leucine incorporation into polypeptides were studied,using polypeptide synthesizing systems from E.coli,rat liver or rabbit reticulocytes. It was shown that in all three systems thialysine inhibits incorporation of labelled lysine into polypeptides,whereas it is without effect on leucine incorporation. The results obtained are reported in Table II. 

M. Fabry, P. Hermann and I, Rychlik. Poly(A)-directed formation of thialysine oligopeptides in E. coli cell-free system. Collection Czechoslov. Commun., 1977, 42 1077. 

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