Structural basis for light activation of a chloroplast enzyme: the structure of sorghum NADP-malate dehydrogenase in its oxidized form
In: Biochemistry, Jg. 38 (1999-04-09), Heft 14
Online
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Zugriff:
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.
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Structural basis for light activation of a chloroplast enzyme: the structure of sorghum NADP-malate dehydrogenase in its oxidized form
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Autor/in / Beteiligte Person: | Johansson, Kenth ; Ramaswamy, S. ; Issakidis-Bourguet, Emmanuelle ; Saarinen, Markku ; Lemaire-Chamley, Martine ; Miginiac-Maslow, Myroslawa ; Eklund, Hans ; Institut de biotechnologie des plantes (IBP) ; Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS) |
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Zeitschrift: | Biochemistry, Jg. 38 (1999-04-09), Heft 14 |
Veröffentlichung: | 1999 |
Medientyp: | unknown |
ISSN: | 0006-2960 (print) ; 1520-4995 (print) |
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