The cysteine synthase complex from plants. Mitochondrial serine acetyltransferase from Arabidopsis thaliana carries a bifunctional domain for catalysis and protein-protein interaction

Eur J Biochem. 2001 Feb;268(3):686-93. doi: 10.1046/j.1432-1327.2001.01920.x.


Serine acetyltransferase (SAT) catalyzes the rate-limiting step of cysteine biosynthesis in bacteria and plants and functions in association with O-acetylserine (thiol) lyase (OAS-TL) in the cysteine synthase complex. Very little is known about the structure and catalysis of SATs except that they share a characteristic C-terminal hexapeptide-repeat domain with a number of enzymatically unrelated acyltransferases. Computational modeling of this domain was performed for the mitochondrial SAT isoform from Arabidopsis thaliana, based on crystal structures of bacterial acyltransferases. The results indicate a left-handed parallel beta-helix consisting of beta-sheets alternating with turns, resulting in a prism-like structure. This model was challenged by site-directed mutagenesis and tested for a suspected dual function of this domain in catalysis and hetero-oligomerization. The bifunctionality of the SAT C-terminus in transferase activity and interaction with OAS-TL is demonstrated and discussed with respect to the putative role of the cysteine synthase complex in regulation of cysteine biosynthesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetyltransferases / chemistry*
  • Amino Acid Sequence
  • Arabidopsis / enzymology*
  • Carbon-Oxygen Lyases / metabolism
  • Catalysis
  • Chromatography, Affinity
  • Cloning, Molecular
  • Cysteine Synthase / chemistry*
  • Cysteine Synthase / genetics
  • Cysteine Synthase / physiology*
  • DNA Mutational Analysis
  • Databases, Factual
  • Electrophoresis, Polyacrylamide Gel
  • Escherichia coli / enzymology
  • Genetic Complementation Test
  • Kinetics
  • Mitochondria / enzymology*
  • Models, Genetic
  • Models, Molecular
  • Molecular Sequence Data
  • Multienzyme Complexes*
  • Mutagenesis, Site-Directed
  • Plants / enzymology*
  • Plasmids / metabolism
  • Protein Binding
  • Protein Structure, Tertiary
  • Saccharomyces cerevisiae Proteins*
  • Sequence Homology, Amino Acid
  • Serine O-Acetyltransferase
  • Software
  • Two-Hybrid System Techniques


  • Multienzyme Complexes
  • Saccharomyces cerevisiae Proteins
  • Acetyltransferases
  • Serine O-Acetyltransferase
  • Cysteine Synthase
  • MET17 protein, S cerevisiae
  • O-acetylhomoserine (thiol)-lyase
  • Carbon-Oxygen Lyases