title: Expression of holo-proteorhodopsin in Synechocystis sp. PCC 6803.
abstract: Retinal-based photosynthesis may contribute to the free energy conversion needed for growth of an organism carrying out oxygenic photosynthesis, like a cyanobacterium. After optimization, this may even enhance the overall efficiency of phototrophic growth of such organisms in sustainability applications. As a first step towards this, we here report on functional expression of the archetype proteorhodopsin in Synechocystis sp. PCC 6803. Upon use of the moderate-strength psbA2 promoter, holo-proteorhodopsin is expressed in this cyanobacterium, at a level of up to 10(5) molecules per cell, presumably in a hexameric quaternary structure, and with approximately equal distribution (on a protein-content basis) over the thylakoid and the cytoplasmic membrane fraction. These results also demonstrate that Synechocystis sp. PCC 6803 has the capacity to synthesize all-trans-retinal. Expressing a substantial amount of a heterologous opsin membrane protein causes a substantial growth retardation Synechocystis, as is clear from a strain expressing PROPS, a non-pumping mutant derivative of proteorhodopsin. Relative to this latter strain, proteorhodopsin expression, however, measurably stimulates its growth.
authors: Molecular Microbial Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
authors: Que
authors: Q
authors: Chen
authors: Molecular Microbial Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
authors: Jeroen B
authors: JB
authors: van der Steen
authors: Mass Spectrometry of Biomacromolecules, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
authors: Henk L
authors: HL
authors: Dekker
authors: Biophysical Organic Chemistry, Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands.
authors: Srividya
authors: S
authors: Ganapathy
authors: Biophysical Organic Chemistry, Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands.
authors: Willem J
authors: WJ
authors: de Grip
authors: Molecular Microbial Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands. Electronic address: K.J.Hellingwerf@uva.nl.
authors: Klaas J
authors: KJ
authors: Hellingwerf
mesh_terms: D015870:Gene Expression; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D025604:Rhodopsins, Microbial / Q000096:biosynthesis* / Q000235:genetics; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D025604:Rhodopsins, Microbial; C413548:proteorhodopsin
keywords: All-trans retinal; Apo- and holo-protein; Cytoplasmic membrane; Proton motive force; Proton pump; Thylakoid membrane