Enzymes of cysteine synthesis show extensive and conserved modifications patterns that include N(α)-terminal acetylation.
Biosynthesis of cysteine is a two-step process in higher plants subsequently catalyzed by serine acetyltransferase (SAT) and O-acetylserine (thiol) lyase (OAS-TL) which are present in cytosol, plastids and mitochondria. Recently, the distribution of SAT and OAS-TL in these subcellular compartments was shown to be crucial for efficient cysteine synthesis in Arabidopsis thaliana. In this study, the abundances of OAS-TLs were quantified independently by immunological detection in crude protein extracts and by SAT affinity purification (SAP) of OAS-TL. OAS-TL A and B were evidenced to be the most abundant isoforms in all analyzed tissues, which is consistent with micro array-based transcript analyses. Application of SAP to Arabidopsis revealed significant modification of the major OAS-TL isoforms present in cytosol, plastids and mitochondria into up to seven subspecies. Specific OAS-TL isoforms were found to be differentially modified in the leaves, roots, stem and cell culture. Sulphur deficiency did not alter modification of OAS-TL proteins purified from cell culture that showed the highest complexity of OAS-TL modifications. However, the pattern of OAS-TL modification was found to be stable within an analyzed tissue, pointing not only to a high reproducibility of SAP but likely biological significance of each subspecies. The most abundant OAS-TL subspecies in cytosol and plastids were subject of N-terminal processing followed by acetylation of the newly originated N-terminus. The mode of N(α)-terminal acetylation of OAS-TL and its possible biological function are discussed.
Wirtz
Markus
M
Heidelberg Institute for Plant Sciences, University of Heidelberg, Germany.
Heeg
Corinna
C
Samami
Arman Allboje
AA
Ruppert
Thomas
T
Hell
Rüdiger
R
D000107:Acetylation; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D003545:Cysteine / Q000096:biosynthesis*; D003547:Cysteine Synthase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D003600:Cytosol / Q000201:enzymology; D004591:Electrophoresis, Polyacrylamide Gel; D018506:Gene Expression Regulation, Plant; D007527:Isoenzymes / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D013058:Mass Spectrometry; D008928:Mitochondria / Q000201:enzymology; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000201:enzymology; D018547:Plant Stems / Q000201:enzymology; D018087:Plastids / Q000201:enzymology; D011499:Protein Processing, Post-Translational; D020539:Sequence Analysis, Protein; D051050:Serine O-Acetyltransferase / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism
D029681:Arabidopsis Proteins; D007527:Isoenzymes; D013438:Sulfhydryl Compounds; D013455:Sulfur; D051050:Serine O-Acetyltransferase; D003547:Cysteine Synthase; D003545:Cysteine