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Subcellular Localization of Carotenoid Biosynthesis in Synechocystis sp. PCC 6803.

Zhang L, Selão TT, Selstam E, Norling B - PLoS ONE (2015)

Bottom Line: Carotenoid analysis of different membrane subfractions in Synechocystis sp.PCC6803 shows that "light" plasma membranes have a high carotenoid/protein ratio, when compared to "heavier" plasma membranes or thylakoids.Both enzymes are locally more abundant in plasma membranes than in thylakoids, implying that the plasma membrane has higher synthesis rates of β-carotene precursor molecules and echinenone.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Nanyang Technological University, Singapore.

ABSTRACT
The biosynthesis pathway of carotenoids in cyanobacteria is partly described. However, the subcellular localization of individual steps is so far unknown. Carotenoid analysis of different membrane subfractions in Synechocystis sp. PCC6803 shows that "light" plasma membranes have a high carotenoid/protein ratio, when compared to "heavier" plasma membranes or thylakoids. The localization of CrtQ and CrtO, two well-defined carotenoid synthesis pathway enzymes in Synechocystis, was studied by epitope tagging and western blots. Both enzymes are locally more abundant in plasma membranes than in thylakoids, implying that the plasma membrane has higher synthesis rates of β-carotene precursor molecules and echinenone.

No MeSH data available.


A simplified pathway for carotenoid biosynthesis in Synehocystis.Only enzymes with verified function are included.
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pone.0130904.g001: A simplified pathway for carotenoid biosynthesis in Synehocystis.Only enzymes with verified function are included.

Mentions: The first committed step in carotenoid biosynthesis is the condensation of two molecules of geranylgeranyl pyrophosphate (GGPP) to form phytoene (see Fig 1) [13]. In Synechocystis this reaction is catalysed by phytoene synthase, encoded by the crtB (slr1255) gene [6]. Phytoene is then converted to various carotenes that are substrates for the synthesis of a variety of xanthophylls. Several enzymes have been identified and shown to be involved in the conversion of phytoene to β-carotene via lycopene. CrtP (Slr1254) is a phytoene desaturase synthesizing ζ-carotene, the deletion of which resulted in absence of β-carotene and its derivatives in Synechocystis [14]. ζ-carotene is further desaturated by CrtQ (Slr0940), a ζ-carotene desaturase that synthesizes lycopene [14–16]. Lycopene is the starting compound of various group modifications that produce a large variety of carotenoids with different physical properties. So far, four types of lycopene cyclase have been identified in different groups of bacteria, CrtL [17], CrtY [18,19], heterodimeric CrtY cyclases [20], and CruA/CruP [21]. Though cyclic carotenoids have been detected in Synechocystis, the enzyme responsible for cyclization of lycopene to β–carotene has not yet been positively identified. Sll0254, for instance, was previously reported to function as a lycopene cyclase/oxygenase but no evidence was found for its catalysing β–carotene formation directly [22,23]. β-carotene is further modified by enzymes such as CrtO [24] and CrtR [25], to produce echinenone and zeaxanthin respectively. The crtO (slr0088) gene, encoding the β-carotene ketolase, was previously inactivated in Synechocystis, with the resulting ΔcrtO mutant being unable to synthesize echinenone [24].


Subcellular Localization of Carotenoid Biosynthesis in Synechocystis sp. PCC 6803.

Zhang L, Selão TT, Selstam E, Norling B - PLoS ONE (2015)

A simplified pathway for carotenoid biosynthesis in Synehocystis.Only enzymes with verified function are included.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4470828&req=5

pone.0130904.g001: A simplified pathway for carotenoid biosynthesis in Synehocystis.Only enzymes with verified function are included.
Mentions: The first committed step in carotenoid biosynthesis is the condensation of two molecules of geranylgeranyl pyrophosphate (GGPP) to form phytoene (see Fig 1) [13]. In Synechocystis this reaction is catalysed by phytoene synthase, encoded by the crtB (slr1255) gene [6]. Phytoene is then converted to various carotenes that are substrates for the synthesis of a variety of xanthophylls. Several enzymes have been identified and shown to be involved in the conversion of phytoene to β-carotene via lycopene. CrtP (Slr1254) is a phytoene desaturase synthesizing ζ-carotene, the deletion of which resulted in absence of β-carotene and its derivatives in Synechocystis [14]. ζ-carotene is further desaturated by CrtQ (Slr0940), a ζ-carotene desaturase that synthesizes lycopene [14–16]. Lycopene is the starting compound of various group modifications that produce a large variety of carotenoids with different physical properties. So far, four types of lycopene cyclase have been identified in different groups of bacteria, CrtL [17], CrtY [18,19], heterodimeric CrtY cyclases [20], and CruA/CruP [21]. Though cyclic carotenoids have been detected in Synechocystis, the enzyme responsible for cyclization of lycopene to β–carotene has not yet been positively identified. Sll0254, for instance, was previously reported to function as a lycopene cyclase/oxygenase but no evidence was found for its catalysing β–carotene formation directly [22,23]. β-carotene is further modified by enzymes such as CrtO [24] and CrtR [25], to produce echinenone and zeaxanthin respectively. The crtO (slr0088) gene, encoding the β-carotene ketolase, was previously inactivated in Synechocystis, with the resulting ΔcrtO mutant being unable to synthesize echinenone [24].

Bottom Line: Carotenoid analysis of different membrane subfractions in Synechocystis sp.PCC6803 shows that "light" plasma membranes have a high carotenoid/protein ratio, when compared to "heavier" plasma membranes or thylakoids.Both enzymes are locally more abundant in plasma membranes than in thylakoids, implying that the plasma membrane has higher synthesis rates of β-carotene precursor molecules and echinenone.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, Nanyang Technological University, Singapore.

ABSTRACT
The biosynthesis pathway of carotenoids in cyanobacteria is partly described. However, the subcellular localization of individual steps is so far unknown. Carotenoid analysis of different membrane subfractions in Synechocystis sp. PCC6803 shows that "light" plasma membranes have a high carotenoid/protein ratio, when compared to "heavier" plasma membranes or thylakoids. The localization of CrtQ and CrtO, two well-defined carotenoid synthesis pathway enzymes in Synechocystis, was studied by epitope tagging and western blots. Both enzymes are locally more abundant in plasma membranes than in thylakoids, implying that the plasma membrane has higher synthesis rates of β-carotene precursor molecules and echinenone.

No MeSH data available.