期刊
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
卷 1860, 期 3, 页码 209-223出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.bbabio.2018.11.008
关键词
Rhodobacter sphaeroides; LH2; Bacteriochlorophyll; Chlorophyll; Light harvesting; Ligand binding; Protein engineering
资金
- Biotechnology and Biological Sciences Research Council (BBSRC UK) [BB/M000265/1]
- Photosynthetic Antenna Research Center (PARC) - U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences [DE-SC 0001035]
- U. S. National Science Foundation [MCB-1021725]
- Photosynthetic Systems Program, Division of Chemical Sciences, Geosciences, and Biosciences (CSGB), Office of Basic Energy Sciences of the U.S. Department of Energy [DE-FG02-94ER20137]
- European Commission Marie Sklodowska-Curie Global Fellowship [660652]
- BBSRC [BB/M000265/1] Funding Source: UKRI
- Marie Curie Actions (MSCA) [660652] Funding Source: Marie Curie Actions (MSCA)
The light-harvesting 2 complex (LH2) of the purple phototrophic bacterium Rhodobacter sphaeroides is a highly efficient, light-harvesting antenna that allows growth under a wide-range of light intensities. In order to expand the spectral range of this antenna complex, we first used a series of competition assays to measure the capacity of the non-native pigments 3-acetyl chlorophyll (Chl) a, Chl d, Chlf or bacteriochlorophyll (BChl) b to replace native BChl a in the B800 binding site of LH2. We then adjusted the B800 site and systematically assessed the binding of non-native pigments. We find that Arg (-10) of the LH2 beta polypeptide plays a crucial role in binding specificity, by providing a hydrogen-bond to the 3-acetyl group of native and non-native pigments. Reconstituted LH2 complexes harbouring the series of (B)Chls were examined by transient absorption and steady-state fluorescence spectroscopies. Although slowed 10-fold to similar to 6 ps, energy transfer from Chl a to B850 BChl a remained highly efficient. We measured faster energy-transfer time constants for Chl d (3.5 ps) and Chlf (2.7 ps), which have red-shifted absorption maxima compared to Chl a. BChI b, red-shifted from the native BChI a, gave extremely rapid (<= 0.1 ps) transfer. These results show that modified LH2 complexes, combined with engineered (B)Chl biosynthesis pathways in vivo, have potential for retaining high efficiency whilst acquiring increased spectral range.
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