The regulatory function of the plant cysteine synthase protein complex for cellular cysteine homeostasis
Final Report Abstract
The synthesis of cysteine is located between assimilatory sulfate reduction and downstream pathways leading to numerous and essential sulfur containing compounds. The homeostasis of cysteine is of utmost importance to balance sulfate uptake and reduction with demand by translation, Fe-S clusters and other processes. At the same time the release of H2S in chloroplasts needs to be controlled to avoid its loss but also intoxication of cellular processes. The project provided direct evidence for dynamic association and dissociation of the cysteine synthase complex in dependence on the intermediates sulfide and O-acetylserine operates in vivo and its dependency on the sulfate supply to roots. The importance of mitochondria for cysteine metabolism was demonstrated in several respects. Their relevance as major contributor to O-acetylserine synthesis, the precursor of cysteine, was directly shown using artificial micro RNA lines with altered expression of serine acetyltransferase, the first subunit of the cysteine synthase complex. The combined roles of cysteine synthase complex formation and the modulation of feedback sensitivity of serine acetyltransferase to cysteine was characterized by NMR with isolated mitochondria. The latter were also instrumental in the investigation of sulfide detoxification to prevent inhibition of cytochrome c oxidase. In conclusion, the synthesis of cysteine integrates sulfate assimilation, sulfur sensing and cellular homeostasis via the cysteine synthase complex.
Publications
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(2008) Mitochondrial serine acetyltransferase functions as pacemaker of cysteine synthesis in plant cells. Plant Physiol 148: 1055- 1067
Haas, F.H., Heeg, C., Queiroz, R., Bauer, A., Wirtz, M., Hell, R.
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(2010) Structure and function of the heterooligomeric cysteine synthase complex in plants. J Biol Chem 285: 32810-32817
Wirtz, M., Birke, H., Heeg, C., Mueller, C., Hosp, F., Throm, C., Koenig, S., Feldman-Salit, A., Rippe, K., Petersen, G., Wade, R. C., Rybin, V., Scheffzek, K. and Hell, R.
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(2012) Cysteine biosynthesis, in concert with a novel mechanism, contributes to sulfide detoxification in mitochondria of Arabidopsis thaliana. Biochem J 445: 275-283
Birke, H., Haas, F. H., De Kok, L. J., Balk, J., Wirtz, M. and Hell, R.
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(2012) Mitochondrial cysteine synthase complex regulates O- acetylserine biosynthesis in plants. J Biol Chem 287: 27941-27947
Wirtz, M., Beard, K. F. M., Lee, C. P., Boltz, A., Schwarzlander, M., Fuchs, C., Meyer, A. J., Heeg, C., Sweetlove, L. J., Ratcliffe, R. G. and Hell, R.
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(2013) Successful fertilization requires the presence of at least one major O-acetylserine(thiol)lyase for cysteine synthesis in pollen of Arabidopsis. Plant Physiol 63: 959 – 972
Birke, H., Heeg, C., Wirtz, M., Hell, R.
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(2014) Evidence for several cysteine transport mechanisms in the mitochondrial membranes of Arabidopsis thaliana. Plant Cell Physiol 55: 64–73
Lee, C.-P., Wirtz, M., Hell, R.
