Genetic dissection of cyclic pyranopterin monophosphate biosynthesis in plant mitochondria

Kruse, Inga, Maclean, Andrew E, Hill, Lionel and Balk, Janneke (2018) Genetic dissection of cyclic pyranopterin monophosphate biosynthesis in plant mitochondria. Biochemical Journal, 475 (2). pp. 495-509. ISSN 0264-6021

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Mitochondria play a key role in the biosynthesis of two metal cofactors, iron-sulfur (FeS) clusters and molybdenum cofactor (Moco). The two pathways intersect at several points, but a scarcity of mutants has hindered studies to better understand these links. We screened a collection of sirtinol-resistant Arabidopsis thaliana mutants for lines with decreased activities of cytosolic FeS enzymes and Moco enzymes. We identified a new mutant allele of ATM3 , encoding the ATP-binding cassette Transporter of the Mitochondria 3 (systematic name ABCB25), confirming the previously reported role of ATM3 in both FeS cluster and Moco biosynthesis. We also identified a mutant allele in CNX2, Cofactor of Nitrate reductase and Xanthine dehydrogenase 2 , encoding GTP 3′,8-cyclase, the first step in Moco biosynthesis which is localized in the mitochondria. A single nucleotide polymorphism in cnx2-2 leads to substitution of Arg88 with Gln in the N-terminal FeS cluster-binding motif. cnx2-2 plants are small and chlorotic, with severely decreased Moco enzyme activities, but they performed better than a cnx2-1 knockout mutant, which could only survive with ammonia as nitrogen source. Measurement of cyclic pyranopterin monophosphate (cPMP) levels by LC-MS/MS showed that this Moco intermediate was below the limit of detection in both cnx2-1 and cnx2-2 , and accumulated more than 10-fold in seedlings mutated in the downstream gene CNX5 . Interestingly, atm3-1 mutants had less cPMP than wild type, correlating with previous reports of a similar decrease in nitrate reductase activity. Taken together, our data functionally characterise CNX2 and suggest that ATM3 is indirectly required for cPMP synthesis.

Item Type: Article
Faculty \ School: Faculty of Science > School of Biological Sciences
UEA Research Groups: Faculty of Science > Research Groups > Molecular Microbiology
Faculty of Science > Research Groups > Plant Sciences
Depositing User: Pure Connector
Date Deposited: 26 Jan 2018 11:36
Last Modified: 22 Oct 2022 03:31
DOI: 10.1042/BCJ20170559


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