Excess of charged tRNALys maintains low levels of peptidyl-tRNA hydrolase in pth(Ts) mutants at a non-permissive temperature.
Cellular changes have been monitored during the suppression, mediated by the overproduction of tRNA(Lys), of thermosensitivity in Escherichia coli strain AA7852 carrying a mutation in peptidyl-tRNA hydrolase (Pth) encoded by the pth(Ts) gene. The presence in AA7852 cells of a plasmid bearing lysV gene helped to maintain low levels of the unstable Pth(Ts) protein and to preserve the viability of the mutant line at 41 degrees C whereas plasmids bearing other tRNA genes were ineffective. At 32 degrees C the excess of tRNA(Lys) did not alter the percentages of the free-, charged- or peptidyl-tRNA(Lys) species compared with those found in strains that did not overproduce tRNA(Lys). At 41 degrees C, however, despite increases in the level of peptidyl-tRNA(Lys), the excess tRNA(Lys) helped to maintain the concentration of charged-tRNA(Lys) at a level comparable with that found in non-overproducer cells grown at a permissive temperature. In addition, the excess tRNA(Lys) at 41 degrees C provoked a reduction in the concentrations of various peptidyl-tRNAs, which normally accumulate in pth(Ts) cells, and a proportional increase in the concentrations of the corresponding aminoacyl-tRNAs. The possible mechanism of rescue due to the overexpression of tRNA(Lys) and the causes of tRNA(Lys) starvation in pth(Ts) strains grown at non-permissive temperatures are considered.
Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del IPN Apartado Postal 14-740, 07000 México D.F., México.
Serafin
S
Vivanco-Domínguez
Luis Rogelio
LR
Cruz-Vera
Gabriel
G
Guarneros
D002265:Carboxylic Ester Hydrolases / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D007700:Kinetics; D009154:Mutation; D012346:RNA, Transfer, Amino Acyl / Q000737:chemistry / Q000378:metabolism; D012357:RNA, Transfer, Lys / Q000378:metabolism*; D013696:Temperature
D012346:RNA, Transfer, Amino Acyl; D012357:RNA, Transfer, Lys; D002265:Carboxylic Ester Hydrolases; C019674:aminoacyl-tRNA hydrolase