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Plant Physiology 67:316-324 (1981) © 1981 American Society of Plant Biologists Selenium Metabolism in Neptunia amplexicaulis1School of Environmental and Life Sciences, Murdoch University, Murdoch, Western Australia 6155
ATP sulfurylase (EC 2.7.7.4), cysteinyl-tRNA synthetase (EC 6.1.1.16), and methionyl-tRNA synthetase (EC 6.1.1.10) from Neptunia amplexicaulis have been purified approximately 162-, 140- and 185-fold, respectively. Purified ATP sulfurylase in the presence of purified inorganic pyrophosphatase catalyzed the incorporation of sulfate into adenosine 5'-phosphosulfate; evidence of an analogous reaction with selenate is presented. Crude extracts catalyzed both the sulfate- and the adenosine 5'-phosphosulfate-dependent NADH oxidation in the adenosine 5'-phosphosulfate kinase assay of Burnell and Whatley (1977 Biochim Biophys Acta 481: 266-278), but an analogous reaction with selenate could not be detected. Both purified cysteinyl-tRNA synthetase and methionyl-tRNA synthetase used selenium-containing analogs as substrates in both the ATP-pyrophosphate exchange and the aminoacylation assays. It seems that selenium-containing amino acids are excluded from proteins by a mechanism(s) other than substrate discrimination at the amino acid activation stage of protein synthesis.
1 This research was supported by a grant from the Australian Research Grants Committee. This article has been cited by other articles:
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