9E6M

Crystal structure of the G200R mutant from the maize chloroplastic photosynthetic NADP(+)-dependent malic enzyme

Summary for 9E6M

• Entry DOI: 10.2210/pdb9e6m/pdb
• Related: 5OU5
• Descriptor: Malic enzyme, PYRUVIC ACID (3 entities in total)
• Functional Keywords: malic enzyme, oxidative decarboxylase, nadp-dependent c4 photosynthesis, photosynthesis
• Biological source: Zea mays
• Total number of polymer chains: 4
• Total formula weight: 255506.42

Authors

Klinke, S.,Schneberger, N.,Boehm, J.M.,Willms, S.,Hagelueken, G.,Geyer, M.,Maurino, V.,Alvarez, C.E. (deposition date: 2024-10-30, release date: 2025-01-15, Last modification date: 2026-04-29)

Primary citation

Bohm, J.M.,Willms, S.,Ferrao, O.,Buitrago-Arango, M.,Hudig, M.,Poschmann, G.,Fazelnia, N.,Nagel-Steger, L.,Klinke, S.,Drakonaki, A.,Gatsogiannis, C.,Tronconi, M.A.,Alvarez, C.E.,Maurino, V.G.
A milestone in C4 carbon concentration mechanism evolution: structural remodeling of NADP-malic enzyme in Poaceae.
Mol.Biol.Evol., 43:-, 2026

PubMed Abstract: The evolution of C4 photosynthesis required extensive modification of ancestral enzymes enabling the development of an efficient carbon concentrating mechanism. A key example is NADP-malic enzyme (NADP-ME), which, in maize and sorghum-members of the same C4 lineage-underwent gene duplication and neofunctionalization, resulting in 2 plastidic isoforms with distinct oligomeric states: a tetrameric C4-specific isoform and a dimeric housekeeping (nonC4) isoform. In this study, we resolve the structural basis of this oligomeric divergence using X-ray crystallography, cryo-electron microscopy, and molecular modeling combined with targeted biochemical analysis. Our findings demonstrate that the N-terminal region of nonC4-NADP-ME is involved in its oligomeric organization, whereas a suite of adaptive substitutions at the dimer interface drives the transition to the stable tetramer characteristic of the C4 isoform. Moreover, the C-terminal region stabilizes the oligomeric states of C4- and nonC4-NADP-ME through specific interactions with adaptive residues. We propose that tetramerization mitigates aggregation at the high expression levels demanded by the C4 cycle and likely creates a scaffold for the emergence of regulatory properties. Collectively, the data show that remodeling of terminal domains and inter-subunit interfaces rewires the quaternary architecture of the enzymes, illustrating how subtle structural changes can drive the evolution of complex innovations such as C4 photosynthesis.

PubMed: 42017302
DOI: 10.1093/molbev/msag056

Experimental method

X-RAY DIFFRACTION (2.7 Å)