title: Analysis of photosynthetic complexes from a cyanobacterial ycf37 mutant.
abstract: The Ycf37 protein has been suggested to be involved in the biogenesis and/or stability of the cyanobacterial photosystem I (PSI). With Ycf37 specific antibodies, we analyzed the localization of Ycf37 within the thylakoid membranes of the cyanobacterium Synechocystis sp. PCC 6803. Inspection of a sucrose gradient profile indicated that small amounts of Ycf37 co-fractionated with monomeric photosynthetic complexes, but not with trimeric PSI. Isolating 3xFLAG epitope-tagged Ycf37 by affinity-tag purification rendered several PSI subunits that specifically co-precipitated with this protein. Blue-native PAGE newly revealed two monomeric PSI complexes (PSI and PSI*) in wild-type thylakoids. The lower amount of PsaK present in PSI* may explain its higher electrophoretic mobility. PSI* was more prominent in high-light grown cells and interestingly proved absent in the Deltaycf37 mutant. PSI* appeared again when the mutant was complemented in trans with the wild-type ycf37 gene. In the Deltaycf37 mutant the amount of trimeric PSI complexes was reduced to about 70% of the wild-type level with no significant changes in photochemical activity and subunit composition of the remaining photosystems. Our results indicate that Ycf37 plays a specific role in the preservation of PSI* and the biogenesis of PSI trimers.
authors.affiliation: Institute of Biology, Humboldt University Berlin, Chausseestr. 117, 10115 Berlin, Germany.
authors.forename: Ulf
authors.initials: U
authors.lastname: Dühring
authors.forename: Klaus-Dieter
authors.initials: KD
authors.lastname: Irrgang
authors.forename: Katja
authors.initials: K
authors.lastname: Lünser
authors.forename: Julia
authors.initials: J
authors.lastname: Kehr
authors.forename: Annegret
authors.initials: A
authors.lastname: Wilde
mesh_terms: D001426:Bacterial Proteins / Q000032:analysis* / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D017353:Gene Deletion; D047468:Immunoprecipitation; D045331:Photosystem I Protein Complex / Q000032:analysis* / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D046939:Synechocystis / Q000201:enzymology* / Q000235:genetics; D020524:Thylakoids / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D045331:Photosystem I Protein Complex; D021122:Protein Subunits; C432677:Ycf37 protein, Synechocystis