Light-modulated NADP-malate dehydrogenases from mossfern and green algae: insights into evolution of the enzyme's regulation
Autor(en): | Ocheretina, O Haferkamp, I Tellioglu, H Scheibe, R |
Stichwörter: | CDNA SEQUENCE; chloroplast; CLONING; DEPENDENT ACTIVATION; EXCHANGE; EXPRESSION; Genetics & Heredity; isoenzymes; LEAVES; METABOLITES; molecular evolution; MOTIF; PURIFICATION; redox regulation; SPINACH | Erscheinungsdatum: | 2000 | Herausgeber: | ELSEVIER SCIENCE BV | Enthalten in: | GENE | Band: | 258 | Ausgabe: | 1-2 | Startseite: | 147 | Seitenende: | 154 | Zusammenfassung: | Chloroplast NADP-dependent malate dehydrogenase is one of the best-studied light-regulated enzymes. In C3 plants, NADP-MDH is a part of the `malate valve' that controls the export of reducing equivalents in the form of malate to the cytosol. NADP-MDH is completely inactive in the dark and is activated in the light with reduced thioredoxin. Compared with its permanently active NAD-limited counterparts, NADP-MDH exhibits N- and C-terminal sequence extensions, each bearing one regulatory disulphide. Upon reduction of the C-terminal disulphide, the enzyme active site becomes accessible for the substrate. Reduction of the N-terminal disulphide promotes a conformational change advantageous for catalysis. To trace the evolutionary development of this intricate regulation mechanism, we isolated cDNA clones for NADP-MDH from the mossfern Selaginella and from two unicellular green algae. While the NADP-MDH sequence from Selaginella demonstrates the classic cysteine pattern of the higher plant enzyme, the sequences from the green algae are devoid of the N-terminal regulatory disulphide. Phylogenetic analysis of new sequences and of those available in the databases led to the conclusion that the chloroplast NADP-MDH and the cytosolic NAD-dependent form arose via duplication of an ancestral eubacterial gene, which preceded the separation of plant and animal lineages. Redox-sensitive NADP-MDH activity was detected only in the `green' plant lineage starting from the primitive prasinophytic algae but not in cyanobacteria, Cyanophora paradoxa, red algae and diatoms. The latter organisms therefore appear to utilize mechanisms other than the light-regulated `malate valve' to remove from plastids excessive electrons produced by photosynthesis. (C) 2000 Elsevier Science B.V. All rights reserved. |
ISSN: | 03781119 | DOI: | 10.1016/S0378-1119(00)00409-1 |
Zur Langanzeige
Seitenaufrufe
3
Letzte Woche
0
0
Letzter Monat
2
2
geprüft am 07.06.2024