title: Direct targeting of Arabidopsis cysteine synthase complexes with synthetic polypeptides to selectively deregulate cysteine synthesis.
abstract: Biosynthesis of cysteine is one of the fundamental processes in plants providing the reduced sulfur for cell metabolism. It is accomplished by the sequential action of two enzymes, serine acetyltransferase (SAT) and O-acetylserine (thiol) lyase (OAS-TL). Together they constitute the hetero-oligomeric cysteine synthase (CS) complex through specific protein-protein interactions influencing the rate of cysteine production. The aim of our studies was to deregulate the CS complex formation in order to investigate its function in the control of sulfur homeostasis and optimize cysteine synthesis. Computational modeling was used to build a model of the Arabidopsis thaliana mitochondrial CS complex. Several polypeptides based on OAS-TL C amino-acid sequence found at SAT-OASTL interaction sites were designed as probable competitors for SAT3 binding. After verification of the binding in a yeast two-hybrid assay, the most strongly interacting polypeptide was introduced to different cellular compartments of Arabidopsis cell via genetic transformation. Moderate increase in total SAT and OAS-TL activities, but not thiols content, was observed dependent on the transgenic line and sulfur availability in the hydroponic medium. Though our studies demonstrate the proof of principle, they also suggest more complex interaction of both enzymes underlying the mechanism of their reciprocal regulation.
authors.affiliation: Institute of Biochemistry and Biophysics, Polish Academy of Sciences, Pawińskiego 5A St, 02-106 Warsaw, Poland. blaszczyk@ibb.waw.pl
authors.forename: Anna
authors.initials: A
authors.lastname: Wawrzyńska
authors.forename: Agata
authors.initials: A
authors.lastname: Kurzyk
authors.forename: Monika
authors.initials: M
authors.lastname: Mierzwińska
authors.forename: Danuta
authors.initials: D
authors.lastname: Płochocka
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Wieczorek
authors.forename: Agnieszka
authors.initials: A
authors.lastname: Sirko
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003545:Cysteine / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D003547:Cysteine Synthase / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D012694:Serine / Q000031:analogs & derivatives / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051050:Serine O-Acetyltransferase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: D010455:Peptides; D012694:Serine; D051050:Serine O-Acetyltransferase; D003547:Cysteine Synthase; C043943:O-acetylserine; D003545:Cysteine