title: Interaction of the periplasmic PratA factor and the PsbA (D1) protein during biogenesis of photosystem II in Synechocystis sp. PCC 6803.
abstract: The biogenesis of photosynthetic complexes is assisted by a growing number of trans-acting factors in both chloroplasts and cyanobacteria. We have previously shown that the periplasmic PratA factor from Synechocystis sp. PCC 6803 (Synechocystis 6803) is required for adequate C-terminal processing of the PsbA (D1) subunit of photosystem II (PSII) supporting the idea that the early steps of PSII assembly occur at the plasma membrane. Here we report on the molecular analysis of the interaction between PratA and the D1 protein. Both yeast two-hybrid and glutathione S-transferase pulldown assays revealed that PratA binds to the soluble forms of both mature and precursor D1 C-terminal regions. In agreement with that finding, the binding region was mapped to amino acid positions 314-328 of D1 by applying a peptide-scanning approach. Approximately 10-20% of the soluble PratA factor was found to be associated with membranes in a D1-dependent manner. Sucrose density gradient centrifugations allowed the identification of a specific membrane subfraction that contains both PratA and D1 and which might represent a transfer and/or connecting region between plasma and thylakoid membrane. Imaging data obtained with enhanced cyan fluorescent protein-labeled D1 protein in wild-type and pratA mutant backgrounds further supported this notion.
authors.affiliation: Molekulare Pflanzenwissenschaften, Biozentrum LMU München, Grosshaderner Strasse 2-4, Planegg-Martinsried 82152, Germany.
authors.forename: Marco
authors.initials: M
authors.lastname: Schottkowski
authors.forename: Stephanie
authors.initials: S
authors.lastname: Gkalympoudis
authors.forename: Nevena
authors.initials: N
authors.lastname: Tzekova
authors.forename: Christian
authors.initials: C
authors.lastname: Stelljes
authors.forename: Danja
authors.initials: D
authors.lastname: Schünemann
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Ankele
authors.forename: Jörg
authors.initials: J
authors.lastname: Nickelsen
mesh_terms: D010449:Peptide Mapping / Q000379:methods; D033903:Periplasmic Proteins / Q000235:genetics / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding / Q000502:physiology; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism*; D020524:Thylakoids / Q000201:enzymology* / Q000235:genetics
chemical_list: D033903:Periplasmic Proteins; D045332:Photosystem II Protein Complex; C422369:photosystem II, psbA subunit