title: Synechocystis sp. PCC 6803 CruA (sll0147) encodes lycopene cyclase and requires bound chlorophyll a for activity.
abstract: The genome of the model cyanobacterium, Synechococcus sp. PCC 7002, encodes two paralogs of CruA-type lycopene cyclases, SynPCC7002_A2153 and SynPCC7002_A0043, which are denoted cruA and cruP, respectively. Unlike the wild-type strain, a cruA deletion mutant is light-sensitive, grows slowly, and accumulates lycopene, γ-carotene, and 1-OH-lycopene; however, this strain still produces β-carotene and other carotenoids derived from it. Expression of cruA from Synechocystis sp. PCC 6803 (cruA6803) in Escherichia coli strains that synthesize either lycopene or γ-carotene did not lead to the synthesis of either γ-carotene or β-carotene, respectively. However, expression of this orthologous cruA6803gene (sll0147) in the Synechococcus sp. PCC 7002 cruA deletion mutant produced strains with phenotypic properties identical to the wild type. CruA6803was purified from Synechococcus sp. PCC 7002 by affinity chromatography, and the purified protein was pale yellow-green due to the presence of bound chlorophyll (Chl) a and β-carotene. Native polyacrylamide gel electrophoresis of the partly purified protein in the presence of lithium dodecylsulfate at 4 °C confirmed that the protein was yellow-green in color. When purified CruA6803was assayed in vitro with either lycopene or γ-carotene as substrate, β-carotene was synthesized. These data establish that CruA6803is a lycopene cyclase and that it requires a bound Chl a molecule for activity. Possible binding sites for Chl a and the potential regulatory role of the Chl a in coordination of Chl and carotenoid biosynthesis are discussed.
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Xiong
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA.
authors.forename: Gaozhong
authors.initials: G
authors.lastname: Shen
authors.affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA. dab14@psu.edu.|Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717, USA. dab14@psu.edu.
authors.forename: Donald A
authors.identifier: http://orcid.org/0000-0003-2782-5988
authors.initials: DA
authors.lastname: Bryant
mesh_terms: D000595:Amino Acid Sequence; D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism*; D000077194:Chlorophyll A; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D005798:Genes, Bacterial; D019753:Intramolecular Lyases / Q000737:chemistry / Q000235:genetics*; D000077276:Lycopene; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D046939:Synechocystis / Q000201:enzymology / Q000235:genetics*
chemical_list: D002734:Chlorophyll; D002338:Carotenoids; D019753:Intramolecular Lyases; C070925:lycopene cyclase-isomerase; D000077276:Lycopene; D000077194:Chlorophyll A
keywords: Carotenogenesis; Carotenoids; Chlorophyll; Lycopene cyclase; Photosynthesis; β-Carotene