Expression and biochemical characterization of the 1-HO-carotenoid methylase CrtF from Rhodobacter capsulatus.
In purple bacteria, acyclic 1-methoxy carotenoids like spheroidene or spirilloxanthin are essential components of the photosynthetic apparatus. One of the last steps of their biosynthesis involves O-methylation of the 1-hydroxy group. The 1-HO-carotenoid methylase CrtF from Rhodobacter capsulatus catalyzing this type of reaction was expressed in Escherichia coli in an active form. It was then purified by affinity chromatography and biochemically characterized. The enzymatic reaction depends on S-adenosylmethionine as the only cofactor. By complementation in E. coli, the substrate specificity of the enzyme was determined. It could be shown that the enzyme converts not only all possible 1-hydroxy carotenoids in the spheroidene/1'-HO-spheroidene biosynthetic pathway of R. capsulatus but also carotenoid intermediates leading to the formation of spirilloxanthin in a pathway which is absent in R. capsulatus but present in related species.
Badenhop
Frank
F
Biosynthesis Group, Botanical Institute, J.W. Goethe Universität, P.O. Box 111932, D-60054, Frankfurt/Main, Germany. sadmann@em-uni.frankfurt.de
Steiger
Sabine
S
Sandmann
Manuela
M
Sandmann
Gerhard
G
D002338:Carotenoids / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli; D005816:Genetic Complementation Test; D008745:Methylation; D008780:Methyltransferases / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology; D016354:Rhodobacter capsulatus / Q000201:enzymology* / Q000235:genetics*; D013379:Substrate Specificity
D002338:Carotenoids; D008780:Methyltransferases