Abstract
Import of the precursor to 5-enolpyruvylshikimate-3-phosphate synthase (pEPSPS) into chloroplasts is inhibited by the herbicide glyphosate. Inhibition of import is maximal at glyphosate concentrations of ≥10 μm and occurs only when pEPSPS is present as a ternary complex of enzyme–shikimate-3-phosphate–glyphosate. Glyphosate alone had no effect on the import of pEPSPS since it is not known to interact with the enzyme in the absence of shikimate-3-phosphate. Experiments with wild-type and glyphosate-resistant mutant forms of pEPSPS show that inhibition of import is directly proportional to the binding constants for glyphosate. Inhibition of import is thus a direct consequence of glyphosate binding to the enzyme–shikimate-3-phosphate complex. The potential for non-specific effects of glyphosate on the chloroplast transport mechanism has been discounted by showing that import of another chloroplast-designated protein was unaffected by high concentrations of glyphosate and shikimate-3-phosphate. The mechanism of import inhibition by glyphosate is consistent with a precursor unfolding/refolding model.
Keywords: EPSP synthase, shikimate pathway, transit peptide
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- Boocock M. R., Coggins J. R. Kinetics of 5-enolpyruvylshikimate-3-phosphate synthase inhibition by glyphosate. FEBS Lett. 1983 Apr 5;154(1):127–133. doi: 10.1016/0014-5793(83)80888-6. [DOI] [PubMed] [Google Scholar]
- Chen W. J., Douglas M. G. Phosphodiester bond cleavage outside mitochondria is required for the completion of protein import into the mitochondrial matrix. Cell. 1987 Jun 5;49(5):651–658. doi: 10.1016/0092-8674(87)90541-1. [DOI] [PubMed] [Google Scholar]
- Chua N. H., Schmidt G. W. Post-translational transport into intact chloroplasts of a precursor to the small subunit of ribulose-1,5-bisphosphate carboxylase. Proc Natl Acad Sci U S A. 1978 Dec;75(12):6110–6114. doi: 10.1073/pnas.75.12.6110. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Della-Cioppa G., Bauer S. C., Klein B. K., Shah D. M., Fraley R. T., Kishore G. M. Translocation of the precursor of 5-enolpyruvylshikimate-3-phosphate synthase into chloroplasts of higher plants in vitro. Proc Natl Acad Sci U S A. 1986 Sep;83(18):6873–6877. doi: 10.1073/pnas.83.18.6873. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Eilers M., Schatz G. Binding of a specific ligand inhibits import of a purified precursor protein into mitochondria. Nature. 1986 Jul 17;322(6076):228–232. doi: 10.1038/322228a0. [DOI] [PubMed] [Google Scholar]
- Flügge U. I., Hinz G. Energy dependence of protein translocation into chloroplasts. Eur J Biochem. 1986 Nov 3;160(3):563–570. doi: 10.1111/j.1432-1033.1986.tb10075.x. [DOI] [PubMed] [Google Scholar]
- Laemmli U. K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4. Nature. 1970 Aug 15;227(5259):680–685. doi: 10.1038/227680a0. [DOI] [PubMed] [Google Scholar]
- Lubben T. H., Bansberg J., Keegstra K. Stop-transfer regions do not halt translocation of proteins into chloroplasts. Science. 1987 Nov 20;238(4830):1112–1114. doi: 10.1126/science.238.4830.1112. [DOI] [PubMed] [Google Scholar]
- Pain D., Blobel G. Protein import into chloroplasts requires a chloroplast ATPase. Proc Natl Acad Sci U S A. 1987 May;84(10):3288–3292. doi: 10.1073/pnas.84.10.3288. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Randall L. L., Hardy S. J. Correlation of competence for export with lack of tertiary structure of the mature species: a study in vivo of maltose-binding protein in E. coli. Cell. 1986 Sep 12;46(6):921–928. doi: 10.1016/0092-8674(86)90074-7. [DOI] [PubMed] [Google Scholar]
- Schleyer M., Neupert W. Transport of proteins into mitochondria: translocational intermediates spanning contact sites between outer and inner membranes. Cell. 1985 Nov;43(1):339–350. doi: 10.1016/0092-8674(85)90039-x. [DOI] [PubMed] [Google Scholar]
- Schmidt G. W., Mishkind M. L. The transport of proteins into chloroplasts. Annu Rev Biochem. 1986;55:879–912. doi: 10.1146/annurev.bi.55.070186.004311. [DOI] [PubMed] [Google Scholar]
- Shah D. M., Horsch R. B., Klee H. J., Kishore G. M., Winter J. A., Tumer N. E., Hironaka C. M., Sanders P. R., Gasser C. S., Aykent S., Siegel N. R., Rogers S. G., Fraley R. T. Engineering herbicide tolerance in transgenic plants. Science. 1986 Jul 25;233(4762):478–481. doi: 10.1126/science.233.4762.478. [DOI] [PubMed] [Google Scholar]
- Steinrücken H. C., Amrhein N. The herbicide glyphosate is a potent inhibitor of 5-enolpyruvyl-shikimic acid-3-phosphate synthase. Biochem Biophys Res Commun. 1980 Jun 30;94(4):1207–1212. doi: 10.1016/0006-291x(80)90547-1. [DOI] [PubMed] [Google Scholar]