General George B. McClellan: Shield of the Union (review)

Rubin, Louis D.

doi:10.1353/cwh.1957.0000

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“…I n some cases, the amount of aminoacyl-tRNA does not reach a plateau value, but reaches a maximum and then decreases, although the enzyme is still active [3,8,12,14].…”

Section: Lo]mentioning

confidence: 99%

Interpretation of Incomplete Reactions in tRNA Aminoacylation

Bonnet¹,

Ebel²

1972

European Journal of Biochemistry

106

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A study has been performed in order to try to explain some anomalies which are observed in aminoacylation reactions : the extent of aminoacylation often depends upon the experimental conditions, such as the enzyme concentration or the ionic strength.We have demonstrated that these anomalies can be explained, in the case of yeast tRh'AT; '-valyl-tRNA synthetase system, by the existence of two reactions occurring beside the aminoacylation reaction : the spontaneous deacylation of the valyl-tRNAV" and a valyl-tRNA synthetase-catalyzed deacylation of the valyl-tRNAVa1. Consequently, any aminoacylation plateau merely reflects the existence of an equilibrium between the aminoacylation reaction and the deacylation reactions.Sometimes the aminoacylation kinetics do not present a plateau but a maximum value followed by a decrease with time. This can be explained by an additional reaction : a valyl-tRNA synthetase-catalyzed degradation of ATP into AMP and PPi in the presence of tRNAVa1 and of valine. This reaction leads to an accumulation of AMP and PPi favouring the reverse reaction of the aminoacylation.The kinetic constants of these reactions have keen determined. Knowing these constants, it is possible to calculate theoretical aminoacylation plateau values which are in good agreement with the experimental ones. These interpretations can probably be extended to all the tRNA aminoacylation systems.Previous results from this laboratory, as well from others, have given evidence from some anomalies in the kinetics of tRNA aminoacylation with aminoacyl-tRNA synthetase.Some

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“…I n some cases, the amount of aminoacyl-tRNA does not reach a plateau value, but reaches a maximum and then decreases, although the enzyme is still active [3,8,12,14].…”

Section: Lo]mentioning

confidence: 99%