Acquirement and characterization of a carotenoid mutant (GM309) of Rhodobacter sphaeroides 601.
A green mutant was obtained among the chemically induced mutants of Rhodobacter sphaeroides 601 (RS601) and named GM309. A blue shift of 20 nm of the carotenoid absorption spectrum was found in the light-harvesting complex II (LH2) of GM309. Different from LH2 of RS601, it was found that the carotenoids in GM309-LH2 changed to be neurosporene by mutation. Neurosporene lacks a conjugate double bond, compared with the spheroidene in RS601-LH2 which has ten conjugate double bonds. As shown by absorption and circular dichroism spectroscopy, the overall structure of GM309-LH2 is little affected by this change. From fluorescence emission spectra, it is found that GM309-LH2 can transfer energy from carotenoids to Bchl-B850 without any change in efficiency. But the efficiency of energy transfer from B800 to B850 in GM309-LH2 is decreased to be 42% of that of the native. This work would provide a novel method to investigate the mechanism of excitation energy transfer in LH2.
Yuan
Liu
L
Shanghai Institute of Plant Physiology & Ecology, Shanghai institute for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Wei
Zhang
Z
Yongqiang
Wu
W
Chunhe
Xu
X
D002338:Carotenoids / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D002942:Circular Dichroism; D045342:Light-Harvesting Protein Complexes / Q000737:chemistry / Q000235:genetics; D009154:Mutation; D010641:Phenotype; D012242:Rhodobacter sphaeroides / Q000235:genetics* / Q000378:metabolism*; D013050:Spectrometry, Fluorescence
D045342:Light-Harvesting Protein Complexes; D002338:Carotenoids; C008604:neurosporene