Lumen Thiol Oxidoreductase1, a disulfide bond-forming catalyst, is required for the assembly of photosystem II in Arabidopsis.
Here, we identify Arabidopsis thaliana Lumen Thiol Oxidoreductase1 (LTO1) as a disulfide bond-forming enzyme in the thylakoid lumen. Using topological reporters in bacteria, we deduced a lumenal location for the redox active domains of the protein. LTO1 can partially substitute for the proteins catalyzing disulfide bond formation in the bacterial periplasm, which is topologically equivalent to the plastid lumen. An insertional mutation within the LTO1 promoter is associated with a severe photoautotrophic growth defect. Measurements of the photosynthetic activity indicate that the lto1 mutant displays a limitation in the electron flow from photosystem II (PSII). In accordance with these measurements, we noted a severe depletion of the structural subunits of PSII but no change in the accumulation of the cytochrome b(6)f complex or photosystem I. In a yeast two-hybrid assay, the thioredoxin-like domain of LTO1 interacts with PsbO, a lumenal PSII subunit known to be disulfide bonded, and a recombinant form of the molecule can introduce a disulfide bond in PsbO in vitro. The documentation of a sulfhydryl-oxidizing activity in the thylakoid lumen further underscores the importance of catalyzed thiol-disulfide chemistry for the biogenesis of the thylakoid compartment.
Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA.
Mohamed
M
Karamoko
Sara
S
Cline
Kevin
K
Redding
Natividad
N
Ruiz
Patrice P
PP
Hamel
D017360:Arabidopsis / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D003001:Cloning, Molecular; D045348:Cytochromes f / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism; D004789:Enzyme Activation; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005816:Genetic Complementation Test; D005822:Genetic Vectors / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010788:Photosynthesis; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism*; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D054730:Protein Interaction Domains and Motifs; D060431:Thylakoid Membrane Proteins / Q000235:genetics / Q000378:metabolism; D020524:Thylakoids / Q000201:enzymology* / Q000378:metabolism; D014170:Transformation, Genetic; D020798:Two-Hybrid System Techniques; D064417:Vitamin K Epoxide Reductases / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D018744:DNA, Plant; D004220:Disulfides; D045332:Photosystem II Protein Complex; D060431:Thylakoid Membrane Proteins; C054266:photosystem II manganese-stabilizing protein; D045348:Cytochromes f; D064417:Vitamin K Epoxide Reductases; C000604454:lumen thiol oxidoreductase 1, Arabidopsis