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

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Abstract

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 species: 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 in planta has remained elusive. Here, we report that accumulation of heme, induced by feeding with ALA, stimulates Clp-protease-dependent degradation of Arabidopsis 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.

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All data generated or analysed during this study are included in the manuscript and supporting files.

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Andreas S Richter

Institute of Biology/Plant Physiology, Humboldt University of Berlin, Berlin, Germany

For correspondence
andreas.richter@hu-berlin.de

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-2293-7297
Claudia Banse

Institute of Biology/Plant Physiology, Humboldt University of Berlin, Berlin, Germany

Competing interests
The authors declare that no competing interests exist.
Bernhard Grimm

Institute of Biology/Plant Physiology, Humboldt University of Berlin, Berlin, Germany

For correspondence
bernhard.grimm@hu-berlin.de

Competing interests
The authors declare that no competing interests exist.

Funding

Deutsche Forschungsgemeinschaft (317556048)

Bernhard Grimm

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.