Details

Autor(en) / Beteiligte

• Kopečná, Martina
• Vigouroux, Armelle
• Vilím, Jan
• Končitíková, Radka
• Briozzo, Pierre
• Hájková, Eva
• Jašková, Lenka
• von Schwartzenberg, Klaus
• Šebela, Marek
• Moréra, Solange
• Kopečný, David

Titel

The ALDH 21 gene found in lower plants and some vascular plants codes for a NADP + ‐dependent succinic semialdehyde dehydrogenase

Ist Teil von

• The Plant journal : for cell and molecular biology, 2017-10, Vol.92 (2), p.229-243

Erscheinungsjahr

2017

Quelle

Wiley Online Library

Beschreibungen/Notizen

• Summary Lower plant species including some green algae, non‐vascular plants (bryophytes) as well as the oldest vascular plants (lycopods) and ferns (monilophytes) possess a unique aldehyde dehydrogenase ( ALDH ) gene named ALDH 21 , which is upregulated during dehydration. However, the gene is absent in flowering plants. Here, we show that ALDH 21 from the moss Physcomitrella patens codes for a tetrameric NADP + ‐dependent succinic semialdehyde dehydrogenase ( SSALDH ), which converts succinic semialdehyde, an intermediate of the γ‐aminobutyric acid ( GABA ) shunt pathway, into succinate in the cytosol. NAD + is a very poor coenzyme for ALDH 21 unlike for mitochondrial SSALDH s ( ALDH 5), which are the closest related ALDH members. Structural comparison between the apoform and the coenzyme complex reveal that NADP + binding induces a conformational change of the loop carrying Arg‐228, which seals the NADP + in the coenzyme cavity via its 2′‐phosphate and α‐phosphate groups. The crystal structure with the bound product succinate shows that its carboxylate group establishes salt bridges with both Arg‐121 and Arg‐457, and a hydrogen bond with Tyr‐296. While both arginine residues are pre‐formed for substrate/product binding, Tyr‐296 moves by more than 1 Å. Both R121A and R457A variants are almost inactive, demonstrating a key role of each arginine in catalysis. Our study implies that bryophytes but presumably also some green algae, lycopods and ferns, which carry both ALDH 21 and ALDH 5 genes, can oxidize SSAL to succinate in both cytosol and mitochondria, indicating a more diverse GABA shunt pathway compared with higher plants carrying only the mitochondrial ALDH 5. Significance Statement The unique aldehyde dehydrogenase ( ALDH ) gene ALDH 21, found in the genomes of lower plants including some green algae, bryophytes as well as the oldest vascular plants and ferns but not in higher plants, is upregulated during dehydration in moss. We cloned the gene, solved the crystal structure of the gene product and characterized the protein as a cytosolic tetrameric NADP +‐dependent succinic semialdehyde dehydrogenase involved in the γ‐aminobutyrate ( GABA ) shunt pathway.