title: NADPH:Protochlorophyllide oxidoreductase uses the general import route into chloroplasts.
abstract: Chloroplast differentiation in angiosperm plants depends on the light-dependent conversion of protochlorophyllide to chlorophyllide by NADPH:protochlorophyllide oxidoreductase (PORA; EC 1.6.99.1), a nuclearly encoded protein. The protein import of the precursor form of PORA into plastids was shown previously to strictly depend on the presence of its substrate protochlorophyllide. PORA seemed to follow a novel, posttranslationally regulated import route. Here we demonstrate that the precursor of PORA from barley is imported into isolated barley plastids independently of protochlorophyllide. PORA as well as PORB import is competed for by the precursor of the small subunit of Rubisco. The data demonstrate that the PORA precursor uses the general import pathway into plastids. Furthermore, en route into chloroplasts the pea POR precursor can be cross-linked to the protein import channel in the outer envelope Toc75 from pea.
authors.affiliation: Department of Plant Physiology, Göteborg University, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Aronsson
authors.forename: K
authors.initials: K
authors.lastname: Sohrt
authors.forename: J
authors.initials: J
authors.lastname: Soll
mesh_terms: D000622:Aminolevulinic Acid / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002736:Chloroplasts / Q000378:metabolism*; D001467:Hordeum / Q000737:chemistry; D008565:Membrane Proteins / Q000378:metabolism; D010088:Oxidoreductases / Q000378:metabolism*; D044925:Oxidoreductases Acting on CH-CH Group Donors; D018532:Pisum sativum / Q000737:chemistry; D017319:Photosensitizing Agents / Q000494:pharmacology; D010940:Plant Proteins / Q000378:metabolism; D018087:Plastids / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D011521:Protochlorophyllide / Q000378:metabolism; D012273:Ribulose-Bisphosphate Carboxylase / Q000378:metabolism
chemical_list: D008565:Membrane Proteins; C103933:OEP75 protein precursor, plant; D017319:Photosensitizing Agents; D010940:Plant Proteins; D011498:Protein Precursors; D011521:Protochlorophyllide; D000622:Aminolevulinic Acid; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C023886:protochlorophyllide reductase; D012273:Ribulose-Bisphosphate Carboxylase