Engineering of B800 bacteriochlorophyll binding site specificity in the <i>Rhodobacter sphaeroides</i> LH2 antenna



Swainsbury, David JK, Faries, Kaitlyn M, Niedzwiedzki, Dariusz M, Martin, Elizabeth C, Flinders, Adam J, Canniffe, Daniel P ORCID: 0000-0002-5022-0437, Shen, Gaozhong, Bryant, Donald A, Kirrnaier, Christine, Holten, Dewey
et al (show 1 more authors) (2019) Engineering of B800 bacteriochlorophyll binding site specificity in the <i>Rhodobacter sphaeroides</i> LH2 antenna. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS, 1860 (3). pp. 209-223.

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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<sub>-10</sub> of the LH2 β 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.

Item Type: Article
Uncontrolled Keywords: Rhodobacter sphaeroides, LH2, Bacteriochlorophyll, Chlorophyll, Light harvesting, Ligand binding, Protein engineering
Depositing User: Symplectic Admin
Date Deposited: 31 May 2019 07:59
Last Modified: 09 Oct 2023 19:58
DOI: 10.1016/j.bbabio.2018.11.008
Open Access URL: https://www.sciencedirect.com/science/article/pii/...
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URI: https://livrepository.liverpool.ac.uk/id/eprint/3043785

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