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Protochlorophyllide synthesis by recombinant cyclases from eukaryotic oxygenic phototrophs and the dependence on Ycf54
The unique isocyclic E ring of chlorophylls contributes to their role as light-absorbing pigments in photosynthesis. The formation of the E ring is catalyzed by the Mg-protoporphyrin IX monomethyl ester cyclase, and the O(2)-dependent cyclase in prokaryotes consists of a diiron protein AcsF, augment...
Autores principales: | , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Portland Press Ltd.
2020
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7319587/ https://www.ncbi.nlm.nih.gov/pubmed/32469391 http://dx.doi.org/10.1042/BCJ20200221 |
Sumario: | The unique isocyclic E ring of chlorophylls contributes to their role as light-absorbing pigments in photosynthesis. The formation of the E ring is catalyzed by the Mg-protoporphyrin IX monomethyl ester cyclase, and the O(2)-dependent cyclase in prokaryotes consists of a diiron protein AcsF, augmented in cyanobacteria by an auxiliary subunit Ycf54. Here, we establish the composition of plant and algal cyclases, by demonstrating the in vivo heterologous activity of O(2)-dependent cyclases from the green alga Chlamydomonas reinhardtii and the model plant Arabidopsis thaliana in the anoxygenic photosynthetic bacterium Rubrivivax gelatinosus and in the non-photosynthetic bacterium Escherichia coli. In each case, an AcsF homolog is the core catalytic subunit, but there is an absolute requirement for an algal/plant counterpart of Ycf54, so the necessity for an auxiliary subunit is ubiquitous among oxygenic phototrophs. A C-terminal ∼40 aa extension, which is present specifically in green algal and plant Ycf54 proteins, may play an important role in the normal function of the protein as a cyclase subunit. |
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