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Nat Plants. 2019 Jul;5(7):755-765. doi: 10.1038/s41477-019-0451-7. Epub 2019 Jun 24.

Molecular adaptations of NADP-malic enzyme for its function in C4 photosynthesis in grasses.

Author information

1
Centro de Estudios Fotosinteticos y Bioquimicos (CEFOBI-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, University of Rosario, Rosario, Argentina.
2
Plant Molecular Physiology and Biotechnology Group, Institute of Developmental and Molecular Biology of Plants, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
3
Cluster of Excellence on Plant Sciences, Düsseldorf, Germany.
4
Center for Structural Studies, Hreinrich Heine University Düsseldorf, Düsseldorf, Germany.
5
Laboratory of Molecular and Structural Microbiology, Institut Pasteur de Montevideo, Montevideo, Uruguay.
6
Institut für Physikalische Biologie, Heinrich Heine University, Düsseldorf, Germany.
7
Institut of Complex Systems, Structural Biochemistry (ICS-6), Jülich, Germany.
8
Integrative Microbiology of Zoonotic Agents, Department of Microbiology, Institut Pasteur, Paris, France.
9
Institute for Computer Science and Department of Biology, Heinrich Heine University Düsseldorf, Düsseldorf, Germany.
10
Plant Molecular Physiology and Biotechnology Group, Institute of Developmental and Molecular Biology of Plants, Heinrich Heine University Düsseldorf, Düsseldorf, Germany. veronica.maurino@uni-duesseldorf.de.
11
Cluster of Excellence on Plant Sciences, Düsseldorf, Germany. veronica.maurino@uni-duesseldorf.de.

Abstract

In C4 grasses of agronomical interest, malate shuttled into the bundle sheath cells is decarboxylated mainly by nicotinamide adenine dinucleotide phosphate (NADP)-malic enzyme (C4-NADP-ME). The activity of C4-NADP-ME was optimized by natural selection to efficiently deliver CO2 to Rubisco. During its evolution from a plastidic non-photosynthetic NADP-ME, C4-NADP-ME acquired increased catalytic efficiency, tetrameric structure and pH-dependent inhibition by its substrate malate. Here, we identified specific amino acids important for these C4 adaptions based on strict differential conservation of amino acids, combined with solving the crystal structures of maize and sorghum C4-NADP-ME. Site-directed mutagenesis and structural analyses show that Q503, L544 and E339 are involved in catalytic efficiency; E339 confers pH-dependent regulation by malate, F140 is critical for the stabilization of the oligomeric structure and the N-terminal region is involved in tetramerization. Together, the identified molecular adaptations form the basis for the efficient catalysis and regulation of one of the central biochemical steps in C4 metabolism.

PMID:
31235877
DOI:
10.1038/s41477-019-0451-7

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