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GrainGenes Reference Report: TPJ-24-297

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Reference	TPJ-24-297
Title	Association of the NADPH:protochlorophyllide oxidoreductase (POR) with isolated etioplast inner membranes from wheat
Journal	The Plant Journal
Year	2001
Pages	297-304
Author	Engdahl S Aronsson H Sundqvist C Timko MP Dahlin C
Abstract	Summary: Membrane association of NADPH:protochlorophyllide oxidoreductase (POR, EC: 1.6.99.1) with isolated prolamellar bodies (PLBs) and prothylakoids (PTs) from wheat etioplasts was investigated. In vitro-expressed radiolabelled POR, with or without transit peptide, was fused to characterize membrane association conditions. Proper association of POR with PLBs and PTs did not require the presequence, whereas NADPH and hydrolysable ATP were vital for the process. After treating the membranes with thermolysin, sodium hydroxide or carbonate, a firm attachment of the POR protein to the membrane was found. Although the PLBs and PTs differ significantly in their relative amount of POR in vivo, no major differences in POR association capacity could be observed between the two membrane systems when exogenous NADPH was added. Experiments run with only an endogenous NADPH source almost abolished association of POR with both PLBs and PTs. In addition, POR protein carrying a mutation in the putative nucleotide-binding site (ALA06) was unable to bind to the inner membranes in the presence of NADPH, which further demonstrates that the co-factor is essential for proper membrane association. POR protein carrying a mutation in the substrate-binding site (ALA24) showed less binding to the membranes as compared to the wild type. The results presented here introduce studies of a novel area of protein-membrane interaction, namely the association of proteins with a paracrystalline membrane structure, the PLB
Keyword	[ Hide all but 1 of 42 ] addition association atp attachment binding binding sites bodies capacity cell membranes cofactor dna binding motifs etioplast in vivo interaction membrane mutation nadph nucleotide binding nucleotide binding site nucleotide sequences oxidoreductase peptide por prolamellar body protein prothylakoids protochlorophyllides site sodium source structure substrate-binding substrate-binding site system thylakoids transit transit peptide triticum aestivum vivo wheat wild wild-type

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