title: Tat-dependent targeting of Rieske iron-sulphur proteins to both the plasma and thylakoid membranes in the cyanobacterium Synechocystis PCC6803.
abstract: Cyanobacteria possess a differentiated membrane system and transport proteins into both the periplasm and thylakoid lumen. We have used green fluorescent protein (GFP)-tagged constructs to study the Tat protein transporter and Rieske Tat substrates in Synechocystis PCC6803. The Tat system has been shown to operate in the plasma membrane; we show here that it is also relatively abundant in the thylakoid membrane network, indicating that newly synthesized Tat substrates are targeted to both membrane systems. Synechocystis contains three Rieske iron-sulphur proteins, all of which contain typical twin-arginine signal-like sequences at their N-termini. We show that two of these proteins (PetC1 and PetC2) are obligate Tat substrates when expressed in Escherichia coli. The Rieske proteins exhibit differential localization in Synechocystis 6803; PetC1 and PetC2 are located in the thylakoid membrane, while PetC3 is primarily targeted to the plasma membrane. The combined data show that Tat substrates are directed with high precision to both membrane systems in this cyanobacterium, raising the question of how, and when, intracellular sorting to the correct membrane is achieved.
authors.affiliation: Department of Biological Sciences, University of Warwick, Coventry, UK.
authors.forename: Cassie
authors.initials: C
authors.lastname: Aldridge
authors.forename: Edward
authors.initials: E
authors.lastname: Spence
authors.forename: Markus A
authors.initials: MA
authors.lastname: Kirkilionis
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Frigerio
authors.forename: Colin
authors.initials: C
authors.lastname: Robinson
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D014450:Electron Transport Complex III / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005816:Genetic Complementation Test; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D010957:Plasmids; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism*; D020524:Thylakoids / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D026901:Membrane Transport Proteins; D011993:Recombinant Fusion Proteins; C037989:Rieske iron-sulfur protein; D049452:Green Fluorescent Proteins; D014450:Electron Transport Complex III