The C-terminus of PufX plays a key role in dimerisation and assembly of the reaction center light-harvesting 1 complex from Rhodobacter sphaeroides.

Autor: Qian P; Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom., Martin EC; Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom., Ng IW; Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom., Hunter CN; Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, United Kingdom. Electronic address: c.n.hunter@sheffield.ac.uk.
Jazyk: angličtina
Zdroj: Biochimica et biophysica acta. Bioenergetics [Biochim Biophys Acta Bioenerg] 2017 Sep; Vol. 1858 (9), pp. 795-803. Date of Electronic Publication: 2017 Jun 03.
DOI: 10.1016/j.bbabio.2017.06.001
Abstrakt: In bacterial photosynthesis reaction center-light-harvesting 1 (RC-LH1) complexes trap absorbed solar energy by generating a charge separated state. Subsequent electron and proton transfers form a quinol, destined to diffuse to the cytochrome bc 1 complex. In bacteria such as Rhodobacter (Rba.) sphaeroides and Rba. capsulatus the PufX polypeptide creates a channel for quinone/quinol traffic across the LH1 complex that surrounds the RC, and it is therefore essential for photosynthetic growth. PufX also plays a key role in dimerization of the RC-LH1-PufX core complex, and the structure of the Rba. sphaeroides complex shows that the PufX C-terminus, particularly the region from X49-X53, likely mediates association of core monomers. To investigate this putative interaction we analysed mutations PufX R49L, PufX R53L, PufX R49/53L and PufX G52L by measuring photosynthetic growth, fractionation of detergent-solubilised membranes, formation of 2-D crystals and electron microscopy. We show that these mutations do not affect assembly of PufX within the core or photosynthetic growth but they do prevent dimerization, consistent with predictions from the RC-LH1-PufX structure. We obtained low resolution structures of monomeric core complexes with and without PufX, using electron microscopy of negatively stained single particles and 3D reconstruction; the monomeric complex with PufX corresponds to one half of the dimer structure whereas LH1 completely encloses the RC if the gene encoding PufX is deleted. On the basis of the insights gained from these mutagenesis and structural analyses we propose a sequence for assembly of the dimeric RC-LH1-PufX complex.
(Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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