PMID:19666483

Citation	Onda, Y, Kumamaru, T and Kawagoe, Y (2009) ER membrane-localized oxidoreductase Ero1 is required for disulfide bond formation in the rice endosperm. Proc. Natl. Acad. Sci. U.S.A. 106:14156-61
Abstract	The developing endosperm of rice (Oryza sativa, Os) synthesizes a large amount of storage proteins on the rough (r)ER. The major storage proteins, glutelins and prolamins, contain either intra or intermolecular disulfide bonds, and oxidative protein folding is necessary for the sorting of the proteins to the protein bodies. Here, we investigated an electron transfer pathway for the formation of protein disulfide bonds in the rER of the rice endosperm, focusing on the roles of the thiol-disulfide oxidoreductase, OsEro1. Confocal microscopic analysis revealed that N-glycosylated OsEro1 is localized to the rER membrane in the subaleurone cells, and that targeting of OsEro1 to the rER membrane depends on the N-terminal region from Met-1 to Ser-55. The RNAi knockdown of OsERO1 inhibited the formation of native disulfide bonds in the glutelin precursors (proglutelins) and promoted aggregation of the proglutelins through nonnative intermolecular disulfide bonds in the rER. Inhibition of the formation of native disulfide bonds was also observed in the seeds of the esp2 mutant, which lacks protein disulfide isomerase-like (PDIL)1;1, but shows enhanced OsEro1 expression. We detected the generation of H(2)O(2) in the rER of the WT subaleurone cells, whereas the rER-derived H(2)O(2) levels decreased markedly in EM49 homozygous mutant seeds, which have fewer sulfhydryl groups than the WT seeds. Together, we propose that the formation of native disulfide bonds in proglutelins depends on an electron transfer pathway involving OsEro1 and OsPDIL.
Links	PubMed PMC2729036 Online version:10.1073/pnas.0904429106
Keywords	Disulfides/chemistry; Electrophoresis, Polyacrylamide Gel; Endoplasmic Reticulum/enzymology; Endoplasmic Reticulum/metabolism; Genes, Plant; Glycosylation; Homozygote; Hydrogen Peroxide/chemistry; Membrane Proteins/genetics; Membrane Proteins/physiology; Microscopy, Confocal/methods; Oryza sativa/enzymology; Oryza sativa/genetics; Peptides/chemistry; Plant Proteins/genetics; Plant Proteins/physiology; Protein Disulfide Reductase (Glutathione)/genetics; Protein Disulfide Reductase (Glutathione)/physiology; Protein Structure, Tertiary; RNA Interference; Subcellular Fractions
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
ORYSJ:Q6AVU2		GO:0005789: endoplasmic reticulum membrane	ECO:0000314:		C		Figure 1 shows OsEro1 colocalizes with the dye that localizes to the ER membrane, GFP-Sec61β.	complete CACAO 5546
ORYSJ:Q6AVU2		GO:0051604: protein maturation	ECO:0000315:		P		Figure 5B and 6A show that proglutelin accumulates in ero1 mutants and because it does not mature into its alpha- and beta-subunits.	complete CACAO 5547
ORYSJ:Q6AVU2	part_of	GO:0005789: endoplasmic reticulum membrane	ECO:0000314: direct assay evidence used in manual assertion		C		Seeded From UniProt	complete
ORYSJ:Q6AVU2	involved_in	GO:0051604: protein maturation	ECO:0000315: mutant phenotype evidence used in manual assertion		P		Seeded From UniProt	complete

References

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