抄録
Several spontaneous revertants able to grow in restrictive temperature (39°C) were isolated from a temperature-sensitive mutant (ts3) of murine leukemic cells L5178Y. The revertants showed reduced plating effi-ciencies and prolonged doubling times at 39°C when compared with wild type cells. The alanyl-tRNA synthetase activity was thermolabile in both ts3 cells and the revertants, indicating suppression as the mechanism of reversion. It was also demonstrated that glycerol protected the enzyme from thermal inac-tivation. The specific activities of alanyl-tRNA synthetase and alanine amino-transferase did not differ much in the wild type, mutant, and revertant cells. This indicates the unlikelihood of thermolabile enzyme overproduction or of increased intracellular concentration of L-alanine causing phenotypic suppres-sion in these revertants. The mechanism of sunnressinn is discussed.
