title: The HCF136 protein is essential for assembly of the photosystem II reaction center in Arabidopsis thaliana.
abstract: Hcf136 encodes a hydrophilic protein localized in the lumen of stroma thylakoids. Its mutational inactivation in Arabidopsis thaliana results in a photosystem II (PHII)-less phenotype. Under standard illumination, PSII is not detectable and the amount of photosystem I (PSI) is reduced, which implies that HCF136p may be required for photosystem biogenesis in general. However, at low light, a comparison of mutants with defects in PSII, PSI, and the cytochrome b(6)f complex reveals that HCF136p regulates selectively biogenesis of PSII. We demonstrate by in vivo radiolabeling of hcf136 that biogenesis of the reaction center (RC) of PSII is blocked. Gel blot analysis and affinity chromatography of solubilized thylakoid membranes suggest that HCF136p associates with a PSII precomplex containing at least D2 and cytochrome b(559). We conclude that HCF136p is essential for assembly of the RC of PSII and discuss its function as a chaperone-like assembly factor.
authors.affiliation: Institut für Entwicklungs, Heinrich-Heine-Universität, Universitätsstrasse 1, 40225 Düsseldorf, Germany.
authors.forename: Henning
authors.initials: H
authors.lastname: Plücken
authors.forename: Bernd
authors.initials: B
authors.lastname: Müller
authors.forename: Dina
authors.initials: D
authors.lastname: Grohmann
authors.forename: Peter
authors.initials: P
authors.lastname: Westhoff
authors.forename: Lutz A
authors.initials: LA
authors.lastname: Eichacker
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins; D003573:Cytochrome b Group / Q000378:metabolism; D045346:Cytochrome b6f Complex; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D008565:Membrane Proteins / Q000235:genetics / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation; D045322:Photosynthetic Reaction Center Complex Proteins / Q000378:metabolism*; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020524:Thylakoids / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D003573:Cytochrome b Group; C115034:HCF136 protein, Arabidopsis; D008565:Membrane Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D011993:Recombinant Fusion Proteins; D045346:Cytochrome b6f Complex