7MDH

STRUCTURAL BASIS FOR LIGHT ACITVATION OF A CHLOROPLAST ENZYME. THE STRUCTURE OF SORGHUM NADP-MALATE DEHYDROGENASE IN ITS OXIDIZED FORM

Summary for 7MDH

• Entry DOI: 10.2210/pdb7mdh/pdb
• Descriptor: PROTEIN (MALATE DEHYDROGENASE), ZINC ION (3 entities in total)
• Functional Keywords: chloroplastic malate dehydrogenase (nadp+), activated by light, chloroplastic malate dehydrogenase
• Biological source: Sorghum bicolor (sorghum)
• Cellular location: Plastid, chloroplast: P17606
• Total number of polymer chains: 4
• Total formula weight: 164577.66

Authors

Johansson, K.,Ramaswamy, S.,Saarinen, M.,Lemaire-Chamley, M.,Issakidis-Bourguet, E.,Miginiac-Maslow, M.,Eklund, H. (deposition date: 1999-02-16, release date: 1999-06-04, Last modification date: 2024-10-30)

Primary citation

Johansson, K.,Ramaswamy, S.,Saarinen, M.,Lemaire-Chamley, M.,Issakidis-Bourguet, E.,Miginiac-Maslow, M.,Eklund, H.
Structural basis for light activation of a chloroplast enzyme: the structure of sorghum NADP-malate dehydrogenase in its oxidized form.
Biochemistry, 38:4319-4326, 1999

PubMed Abstract: Some key chloroplast enzymes are activated by light via a ferredoxin-thioredoxin reduction system which reduces disulfide bridges in the enzymes. We describe for the first time the structural basis for the redox activation of a chloroplast enzyme, the NADP-dependent malate dehydrogenase (MDH) from Sorghum vulgare whose structure has been determined and refined at 2.4 A resolution. In addition to the normal structural components of MDHs, the enzyme exhibits extensions at both the N- and C-termini, each of which contains a regulatory disulfide bridge which must be reduced for activation. The N-terminal disulfide motif is inserted in a cleft between the two subunits of the dimer, thereby locking the domains in each subunit. The C-terminal disulfide keeps the C-terminal residues tight to the enzyme surface and blocks access to the active site. Reduction of the N-terminal disulfide would release the stopper between the domains and give the enzyme the necessary flexibility. Simultaneous reduction of the C-terminal disulfide would free the C-terminal residues from binding to the enzyme and make the active site accessible.

PubMed: 10194350
DOI: 10.1021/bi982876c

Experimental method

X-RAY DIFFRACTION (2.4 Å)