Characterization of the chlorosome antenna of the filamentous anoxygenic phototrophic bacterium Chloronema sp. strain UdG9001 |
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| Authors: | Frederic?Gich,Ruth?L.?Airs,Marianne?Danielsen,Brendan?J.?Keely,Carles?A.?Abella,Jesús?Garcia-Gil,Mette?Miller,Carles?M.?Borrego author-information" > author-information__contact u-icon-before" > mailto:carles.borrego@udg.es" title=" carles.borrego@udg.es" itemprop=" email" data-track=" click" data-track-action=" Email author" data-track-label=" " >Email author |
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| Affiliation: | (1) Institut für Genetik und Mikrobiologie, Ludwig-Maximilians-Universität München, Maria-Ward Strasse 1a, 80638 Munich, Germany;(2) Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL4 7DZ, UK;(3) Dept. of Biochemistry and Molecular Biology, SDU Odense University, Campusvej 55, 5230 Odense M, Denmark;(4) Department of Chemistry, University of York, York YO10 5DD, Heslington, UK;(5) Institute of Aquatic Ecology, University of Girona, Campus de Montilivi, 17071 Girona, Spain |
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| Abstract: | The absorption and fluorescence properties of chlorosomes of the filamentous anoxygenic phototrophic bacterium Chloronema sp. strain UdG9001 were analyzed. The chlorosome antenna of Chloronema consists of bacteriochlorophyll (BChl) d and BChl c together with  -carotene as the main carotenoid. HPLC analysis combined with APCI LC-MS/MS showed that the chlorosomal BChls comprise a highly diverse array of homologues that differ in both the degree of alkylation of the macrocycle at C-8 and/or C-12 and the alcohol moiety esterified to the propionic acid group at C-17. BChl c and BChl d from Chloronema were mainly esterified with geranylgeraniol (33% of the total), heptadecanol (24%), octadecenol (19%), octadecanol (14%), and hexadecenol (9%). Despite this pigment heterogeneity, fluorescence emission of the chlorosomes showed a single peak centered at 765 nm upon excitation at wavelengths ranging from 710 to 740 nm. This single emission, assigned to BChl c, indicates an energy transfer from BChl d to BChl c within the same chlorosome. Likewise, incubation of chlorosomes under reducing conditions caused a weak increase in fluorescence emission, which indicates a small redox-dependent fluorescence. Finally, protein analysis of Chloronema chlorosomes using SDS-PAGE and MALDI-TOF-MS revealed the presence of a chlorosomal polypeptide with a molecular mass of 5.7 kDa, resembling the CsmA protein found in Chloroflexus aurantiacus and Chlorobium tepidum chlorosomes. Several minor polypeptides were also detected but not identified. These results indicate that, compared with other members of filamentous anoxygenic phototrophic bacteria and green sulfur bacteria, Chloronema possesses an antenna system with novel features that may be of interest for further investigations.Abbreviations APCI LC-MS/MS Atmospheric pressure chemical ionization liquid chromatography mass spectrometry - BChl Bacteriochlorophyll - Chl. Chlorobium - Cfl. Chloroflexus - MALDI-TOF-MS Matrix assisted laser desorption/ionization time-of-flight mass spectrometry - [Et] Ethyl - [i-Bu] Isobutyl - [Me] Methyl - [neo-Pent] Neopentyl - [n-Pr] Propyl - t R Retention time |
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| Keywords: | Antenna pigments Bacteriochlorophyll homologues Chloronema Chlorosomes Filamentous anoxygenic phototrophic bacteria Green sulfur bacteria |
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