Modulation of Escherichia coli serine acetyltransferase catalytic activity in the cysteine synthase complex.
In bacteria and plants, serine acetyltransferase (CysE) and O-acetylserine sulfhydrylase-A sulfhydrylase (CysK) collaborate to synthesize l-Cys from l-Ser. CysE and CysK bind one another with high affinity to form the cysteine synthase complex (CSC). We demonstrate that bacterial CysE is activated when bound to CysK. CysE activation results from the release of substrate inhibition, with the Kifor l-Ser increasing from 4 mm for free CysE to 16 mm for the CSC. Feedback inhibition of CysE by l-Cys is also relieved in the bacterial CSC. These findings suggest that the CysE active site is allosterically altered by CysK to alleviate substrate and feedback inhibition in the context of the CSC.
Dipartimento di Medicina e Chirurgia, Università di Parma, Italy.
Roberto
R
Benoni
Dipartimento di Scienze degli Alimenti e del Farmaco, Università di Parma, Italy.
Omar
O
De Bei
Centro Interdipartimentale SITEIA.PARMA, Università di Parma, Italy.
Gianluca
G
Paredi
Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA, USA.|Biomolecular Science and Engineering Program, University of California, Santa Barbara, CA, USA.
Christopher S
CS
Hayes
Dipartimento di Scienze degli Alimenti e del Farmaco, Università di Parma, Italy.
Nina
N
Franko
Dipartimento di Scienze degli Alimenti e del Farmaco, Università di Parma, Italy.|INBB (Istituto Nazionale Biostrutture e Biosistemi), Roma, Italy.|Istituto di Biofisica, CNR, Pisa, Italy.
Andrea
A
Mozzarelli
Dipartimento di Medicina e Chirurgia, Università di Parma, Italy.|INBB (Istituto Nazionale Biostrutture e Biosistemi), Roma, Italy.
Stefano
S
Bettati
Dipartimento di Scienze degli Alimenti e del Farmaco, Università di Parma, Italy.
Barbara
B
Campanini
D000494:Allosteric Regulation; D055162:Biocatalysis; D020134:Catalytic Domain; D003545:Cysteine / Q000378:metabolism*; D003547:Cysteine Synthase / Q000378:metabolism*; D004789:Enzyme Activation; D029968:Escherichia coli Proteins / Q000378:metabolism*; D025461:Feedback, Physiological; D007700:Kinetics; D011485:Protein Binding; D051050:Serine O-Acetyltransferase / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013379:Substrate Specificity
D029968:Escherichia coli Proteins; C070785:CysE protein, E coli; D051050:Serine O-Acetyltransferase; D003547:Cysteine Synthase; D003545:Cysteine
cysteine synthase; protein-protein interaction; serine acetyltransferase