A Zymography technique to study amino acid activation by aminoacyl tRNA synthetases (aaRS): A broad spectrum, high-throughput tool to screen activities of aaRS and their “Urzyme” variants

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Abstract
Amino acyl tRNA synthetases or aaRSs play a key role in assuring the precision of protein translation. They are highly specific for their cognate amino acid and cognate tRNA substrates during protein synthesis, utilizing ATP to ensure that proper assignments are made between amino acid and anticodon. Specific aaRS for each amino acid are present in all cells. We describe a new zymography technique to qualitatively visualize and semi-quantitatively determine the amino acid activation capacity of each type of aaRS molecule by indirect colorimetric detection of released pyrophosphates during the formation of aminoacyl-AMP. Protein samples containing aaRS are subjected to Native PAGE, followed by incubation in buffer containing cognate amino acid and ATP for sufficient time to generate pyrophosphates (PPi) which are then converted to inorganic phosphates by pyrophosphatase treatment. Finally, the generated and localized phosphates around the aaRS protein inside the gel can be visualized after staining by ammonium molybdate and malachite green solution. This technique has been validated by inspecting the substrate specificities of specific aaRSs. This zymography technique is sufficiently sensitive to detect and authenticate activities of much (i.e., ~10 -5 -fold) less active aaRS “Urzymes”, to study alteration of activities of aaRS by various intrinsic or extrinsic factors and to screen aaRS-specific antimicrobial drugs.

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