期刊
FRONTIERS IN MICROBIOLOGY
卷 8, 期 -, 页码 -出版社
FRONTIERS MEDIA SA
DOI: 10.3389/fmicb.2017.00243
关键词
blue light; lyase isomerase; phycobilin; phycourobilin; phycoerythrin; marine cyanobacteria; phycobilisome; marine Synechococcus
类别
资金
- National Institutes of Health Training Grant [T32-GM007757]
- National Science Foundation [MCB-1029414, MCB-1244339]
- Office of the Vice Provost for Research at Indiana University, Bloomington, through its Bridge Funding Program
- Egyptian Cultural and Education Bureau
- Div Of Molecular and Cellular Bioscience
- Direct For Biological Sciences [1244339] Funding Source: National Science Foundation
Marine Synechococcus has successfully adapted to environments with different light colors, which likely contributes to this genus being the second most abundant group of microorganisms worldwide. Populations of Synechococcus that grow in deep, blue ocean waters contain large amounts of the blue-light absorbing chromophore phycourobilin (PUB) in their light harvesting complexes (phycobilisomes). Here, we show that all Synechococcus strains adapted to blue light possess a gene called mpeU. MpeU is structurally similar to phycobilin lyases, enzymes that ligate chromophores to phycobiliproteins. Interruption of mpeU caused a reduction in PUB content, impaired phycobilisome assembly and reduced growth rate more strongly in blue than green light. When mpeU was reintroduced in the mpeU mutant background, the mpeU-less phenotype was complemented in terms of PUB content and phycobilisome content. Fluorescence spectra of mpeU mutant cells and purified phycobilisomes revealed red-shifted phycoerythrin emission peaks, likely indicating a defect in chromophore ligation to phycoerythrin-I (PE-I) or phycoerythrin-II (PE-II). Our results suggest that MpeU is a lyase-isomerase that attaches a phycoerythrobilin to a PEI or PEII subunit and isomerizes it to PUB. MpeU is therefore an important determinant in adaptation of Synechococcus spp. to capture photons in blue light environments throughout the world's oceans.
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