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Structure and function of the hetero-oligomeric cysteine synthase complex in plants

Cysteine synthesis in bacteria and plants is catalyzed by serine acetyltransferase (SAT) and O-acetylserine (thiol)-lyase (OAS-TL), which form the hetero-oligomeric cysteine synthase complex (CSC). In plants, but not in bacteria, the CSC is assumed to control cellular sulfur homeostasis by reversibl...

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Main Authors: Wirtz, Markus (Author) , Birke, Hannah (Author) , Heeg, Corinna (Author) , Müller, Christopher (Author) , Hosp, Fabian (Author) , Throm, Christian (Author) , König, Stephan (Author) , Feldman-Salit, Anna (Author) , Rippe, Karsten (Author) , Petersen, Gabriele (Author) , Wade, Rebecca C. (Author) , Hell, Rüdiger (Author)
Format: Article (Journal)
Language:English
Published: August 18, 2010
In: The journal of biological chemistry
Year: 2010, Volume: 285, Issue: 43, Pages: 32810-32817
ISSN:1083-351X
DOI:10.1074/jbc.M110.157446
Online Access:Verlag, kostenfrei, Volltext: http://dx.doi.org/10.1074/jbc.M110.157446
Verlag, kostenfrei, Volltext: http://www.jbc.org/content/285/43/32810
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Author Notes:Markus Wirtz, Hannah Birke, Corinna Heeg, Christopher Müller, Fabian Hosp, Christian Throm, Stephan König, Anna Feldman-Salit, Karsten Rippe, Gabriele Petersen, Rebecca C. Wade, Vladimir Rybin, Klaus Scheffzek, Rüdiger Hell
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Summary:Cysteine synthesis in bacteria and plants is catalyzed by serine acetyltransferase (SAT) and O-acetylserine (thiol)-lyase (OAS-TL), which form the hetero-oligomeric cysteine synthase complex (CSC). In plants, but not in bacteria, the CSC is assumed to control cellular sulfur homeostasis by reversible association of the subunits. Application of size exclusion chromatography, analytical ultracentrifugation, and isothermal titration calorimetry revealed a hexameric structure of mitochondrial SAT from Arabidopsis thaliana (AtSATm) and a 2:1 ratio of the OAS-TL dimer to the SAT hexamer in the CSC. Comparable results were obtained for the composition of the cytosolic SAT from A. thaliana (AtSATc) and the cytosolic SAT from Glycine max (Glyma16g03080, GmSATc) and their corresponding CSCs. The hexameric SAT structure is also supported by the calculated binding energies between SAT trimers. The interaction sites of dimers of AtSATm trimers are identified using peptide arrays. A negative Gibbs free energy (ΔG = −33 kcal mol−1) explains the spontaneous formation of the AtCSCs, whereas the measured SAT:OAS-TL affinity (KD = 30 nm) is 10 times weaker than that of bacterial CSCs. Free SAT from bacteria is >100-fold more sensitive to feedback inhibition by cysteine than AtSATm/c. The sensitivity of plant SATs to cysteine is further decreased by CSC formation, whereas the feedback inhibition of bacterial SAT by cysteine is not affected by CSC formation. The data demonstrate highly similar quaternary structures of the CSCs from bacteria and plants but emphasize differences with respect to the affinity of CSC formation (KD) and the regulation of cysteine sensitivity of SAT within the CSC.
Item Description:Gesehen am 13.06.2017
Physical Description:Online Resource
ISSN:1083-351X
DOI:10.1074/jbc.M110.157446

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