The GluTR-binding protein is the heme-binding factor for feedback control of glutamyl-tRNA reductase

• Published in: eLife Vol. 8
• Main Authors: Richter, Andreas S, Banse, Claudia, Grimm, Bernhard
• Format: Journal Article
• Language: English
• Published: England eLife Sciences Publications Ltd 13-06-2019; eLife Sciences Publications, Ltd
• Subjects: 5-aminolevulinic acid synthesis; Aldehyde Oxidoreductases - metabolism; Aminolevulinic acid; Aminolevulinic Acid - metabolism; Arabidopsis - metabolism; Arabidopsis Proteins - metabolism; Biodegradation; Biosynthesis; Carrier Proteins - metabolism; Cell Biology; Chlorophyll; Competition; Enzyme Stability; Enzymes; Feedback, Physiological; Gene expression; GluTR; Heme; Heme - metabolism; Isoforms; Light; Metabolome; Mutation - genetics; Plant Biology; Post-translation; posttranslational regulation; Protein Binding; Proteinase; Proteins; Proteolysis; Reductase; tetrapyrrole biosynthesis; tRNA; United States > US; Germany; cell biology; GluTR; heme; tetrapyrrole biosynthesis; A. thaliana; plant biology; 5-aminolevulinic acid synthesis; posttranslational regulation
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/elife.46300

Synthesis of 5-aminolevulinic acid (ALA) is the rate-limiting step in tetrapyrrole biosynthesis in land plants. In photosynthetic eukaryotes and many bacteria, glutamyl-tRNA reductase (GluTR) is the most tightly controlled enzyme upstream of ALA. Higher plants possess two GluTR isoforms: GluTR1 is predominantly expressed in green tissue, and GluTR2 is constitutively expressed in all organs. Although proposed long time ago, the molecular mechanism of heme-dependent inhibition of GluTR
has remained elusive. Here, we report that accumulation of heme, induced by feeding with ALA, stimulates Clp-protease-dependent degradation of
GluTR1. We demonstrate that binding of heme to the GluTR-binding protein (GBP) inhibits interaction of GBP with the N-terminal regulatory domain of GluTR1, thus making it accessible to the Clp protease. The results presented uncover a functional link between heme content and the post-translational control of GluTR stability, which helps to ensure adequate availability of chlorophyll and heme.