The PufX protein of Rhodobacter capsulatus affects the properties of bacterio chlorophyll a and carotenoid pigments of light-harvesting complex 1

被引:16
作者
Aklujkar, M [1 ]
Beatty, JT [1 ]
机构
[1] Univ British Columbia, Dept Microbiol & Immunol, Vancouver, BC V6T 1Z3, Canada
基金
加拿大自然科学与工程研究理事会;
关键词
photosynthesis; purple bacteria; light-harvesting; PufX; Rhodobacter; bacteriochlorophyll; carotenoid;
D O I
10.1016/j.abb.2005.08.018
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
A pufX gene deletion in the purple bacterium Rhodobacter capsulatus causes a severe photosynthetic defect and increases core light-harvesting complex (LH1) protein and bacteriochlorophyll a (BChl) levels. It was suggested that PufX interrupts the LH1 alpha/beta ring around the reaction centre, allowing quinone/quinol exchange. However, naturally PufX(-) purple bacteria grow photosynthetically with an uninterrupted LH1 We discovered that substitutions of the Rhodobacter-specific LH1 alpha seryl-2 decrease carotenoid levels in PufX(-) R. capsulatus. An LH1 alpha S2F mutation improved the photosynthetic growth of a PufX- strain lacking the peripheral LH2 antenna, although LH1 BChl absorption remained above wild-type, suggesting that Rhodobacter-specific carotenoid binding is involved in the PufX(-) photosynthetic defect and LH1 expansion is not. Furthermore, PufX overexpression increased LH1-like BChl absorption without inhibiting photosynthetic growth. PufX(+) LH1 alpha S2-substituted mutant strains had wild-type carotenoid levels, indicating that PufX modulates LH1 carotenoid binding, inducing a conformational change that favours quinone/quinol exchange. (c) 2005 Elsevier Inc. All rights reserved.
引用
收藏
页码:21 / 32
页数:12
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