Enzymes of cysteine synthesis show extensive and conserved modifications patterns that include N(α)-terminal acetylation

• Published in: Amino acids Vol. 39; no. 4; p. 1077
• Main Authors: Wirtz, Markus, Heeg, Corinna, Samami, Arman Allboje, Ruppert, Thomas, Hell, Rüdiger
• Format: Journal Article
• Language: English
• Published: Austria 01.10.2010
• Subjects: Acetylation; Arabidopsis - enzymology; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis Proteins - genetics; Arabidopsis Proteins - metabolism; Cysteine - biosynthesis; Cysteine Synthase - chemistry; Cysteine Synthase - genetics; Cysteine Synthase - isolation & purification; Cysteine Synthase - metabolism; Cytosol - enzymology; Electrophoresis, Polyacrylamide Gel; Gene Expression Regulation, Plant; Isoenzymes - chemistry; Isoenzymes - genetics; Isoenzymes - isolation & purification; Isoenzymes - metabolism; Mass Spectrometry; Mitochondria - enzymology; Plant Leaves - enzymology; Plant Leaves - genetics; Plant Leaves - metabolism; Plant Roots - enzymology; Plant Stems - enzymology; Plastids - enzymology; Protein Processing, Post-Translational; Sequence Analysis, Protein; Serine O-Acetyltransferase - metabolism; Sulfhydryl Compounds - metabolism; Sulfur - metabolism
• DOI: 10.1007/s00726-010-0694-0
• ISSN: 1438-2199

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.