12 



Effects of ^-Fluorophenylalanine on the 

 Growth and Physiology of Yeast 1 



G. N. COHEN H. O. HALVORSON 



Department of Bacteriology, University of Wisconsin 



S. SPIEGELMAN 

 Department of Bacteriology, University of Illinois 



Halvorson and Spiegelman [1] examined a series of amino acid analogs for 

 their ability to inhibit growth of yeast, to deplete the "free amino acid pool," 

 and to synthesize protein. When exponentially growing yeast is washed and 

 resuspended in a nitrogen-free buffer in the presence of glucose, the free amino 

 acids are rapidly incorporated into proteins, thus depleting the amino acid pool. 

 In the presence of high concentrations of ^-fluorophenylalanine (10 -2 M to 

 2X10" 2 M), this depletion is severely inhibited, as shown by chromatographic 

 study of the pool components or by analysis of the glutamic acid content of the 

 pool. This inhibition was interpreted as follows: The presence of an amino 

 acid analog prevents the incorporation not only of its natural homolog but of all 

 the other amino acids as well. 



On the other hand, Munier and Cohen [2] found that /7-fluorophenylalanine, 

 when added to an exponentially growing culture of Escherichia coli, caused a 

 linear growth. During that period the differential rate of incorporation of 

 valine or S 35 



(Avaline or AS 35 ) /Amass 



was the same as in a control culture, although incorporation was somewhat 

 slower than during exponential growth. Radioactive amino acids were formed 



1 This investigation was aided by a grant (G-4258) from the Division of Biological and 

 Medical Sciences of the National Science Foundation. 



100 



