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Engineering of B800 bacteriochlorophyll binding site specificity in the Rhodobacter sphaeroides LH2 antenna.


ABSTRACT: 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, Chl?f 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 ? 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 ~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 Chl?f (2.7?ps), which have red-shifted absorption maxima compared to Chl?a. BChl?b, red-shifted from the native BChl?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.

SUBMITTER: Swainsbury DJK 

PROVIDER: S-EPMC6358721 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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Engineering of B800 bacteriochlorophyll binding site specificity in the Rhodobacter sphaeroides LH2 antenna.

Swainsbury David J K DJK   Faries Kaitlyn M KM   Niedzwiedzki Dariusz M DM   Martin Elizabeth C EC   Flinders Adam J AJ   Canniffe Daniel P DP   Shen Gaozhong G   Bryant Donald A DA   Kirmaier Christine C   Holten Dewey D   Hunter C Neil CN  

Biochimica et biophysica acta. Bioenergetics 20181109 3


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, Chl f or bacteriochlorophyll (BChl) b to replace native BChl a in the B800 binding site of LH2. We  ...[more]

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