期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 114, 期 24, 页码 6280-6285出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1701687114
关键词
photosynthesis; chlorophyll; bacteriochlorophyll; cyclase
资金
- University of Sheffield
- Biotechnology and Biological Sciences Research Council [BB/M000265/1]
- European Research Council [338895]
- European Commission [660652]
- BBSRC [BB/M000265/1] Funding Source: UKRI
- Biotechnology and Biological Sciences Research Council [BB/M000265/1] Funding Source: researchfish
- European Research Council (ERC) [338895] Funding Source: European Research Council (ERC)
- Marie Curie Actions (MSCA) [660652] Funding Source: Marie Curie Actions (MSCA)
The biosynthesis of (bacterio) chlorophyll pigments is among the most productive biological pathways on Earth. Photosynthesis relies on these modified tetrapyrroles for the capture of solar radiation and its conversion to chemical energy. (Bacterio) chlorophylls have an isocyclic fifth ring, the formation of which has remained enigmatic for more than 60 y. This reaction is catalyzed by two unrelated cyclase enzymes using different chemistries. The majority of anoxygenic phototrophic bacteria use BchE, an O-2-sensitive [4Fe-4S] cluster protein, whereas plants, cyanobacteria, and some phototrophic bacteria possess an O-2-dependent enzyme, the major catalytic component of which is a diiron protein, AcsF. Plant and cyanobacterial mutants in ycf54 display impaired function of the O-2-dependent enzyme, accumulating the reaction substrate. Swapping cyclases between cyanobacteria and purple phototrophic bacteria reveals three classes of the O-2-dependent enzyme. AcsF from the purple betaproteobacterium Rubrivivax (Rvi.) gelatinosus rescues the loss not only of its cyanobacterial ortholog, cycI, in Synechocystis sp. PCC 6803, but also of ycf54; conversely, coexpression of cyanobacterial cycI and ycf54 is required to complement the loss of acsF in Rvi. gelatinosus. These results indicate that Ycf54 is a cyclase subunit in oxygenic phototrophs, and that different classes of the enzyme exist based on their requirement for an additional subunit. AcsF is the cyclase in Rvi. gelatinosus, whereas alphaproteobacterial cyclases require a newly discovered protein that we term BciE, encoded by a gene conserved in these organisms. These data delineate three classes of O-2-dependent cyclase in chlorophototrophic organisms from higher plants to bacteria, and their evolution is discussed herein.
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