Molecular approaches towards control of sulfur flux in plants through selective deregulation of cysteine synthase complexes
Final Report Abstract
The plant cysteine synthase complex generates cysteine from serine, acetyl-coenzyme A and sulfide in the cytosol, plastids and mitochondria. The reversible association and dissociation of the constituting enzymes serine acetyltransferase (SAT) and O-acetylserine (thiol) lyase (OAS-TL) and the concomitant changes in enzymatic activity control the rate of cysteine synthesis is response to sulfide and OAS availability. The regulatory function of the cysteine synthase complex was analyzed using a de-regulation approach. Originally based on the model-based design of peptides that interfere with SAT/OAS-TL interaction in vitro and in vivo, the Arabidopsis mitochondrial cysteine synthase complex underwent a detailed and combined experimental and in silico analysis. The quaternary composition, peptide scanning and three-dimensional structure using dynamic modeling revealed an unusual structure with likely only one interaction site on each protein. Sulfide was shown to stabilize the cysteine synthase complex and to be partially detoxified by mitochondrial OAS-TL activity. A combination of reverse genetics and targeted mutation achieved de-regulation the cysteine synthase complex and suggested an additional function of this protein-protein interaction system with respect to cellular sulfur sensing. The proposed functions of the cysteine synthase complex were thus confirmed and complemented by new findings of functions in sulfide scavenging and signaling.
Publications
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(2009) A mechanistic model of the cysteine synthase complex. J Mol Biol 386, 37-59
Feldman-Salit, A., Wirtz, M., Hell, R. and Wade, R. C.
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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) Allosterically gated enzyme dynamics in the cysteine synthase complex regulate cysteine biosynthesis in Arabidopsis thaliana. Structure 20, 292-302
Feldman-Salit, A., Wirtz, M., Lenherr, E. D., Throm, C., Hothorn, M., Scheffzek, K., Hell, R. and Wade, R. C.
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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.
