Institute of Basic Biological Problems of the Russian Academy of Sciences-A Separate Subdivision of PSCBR RAS (IBBP RAS), Pushchino, Moscow Region, Russian Federation.
PeerJ. 2023 Jan 31;11:e14769. doi: 10.7717/peerj.14769. eCollection 2023.
Novel peripheral light-harvesting (LH) complex designated as LL LH2 was isolated along with LH4 complex from cells grown under low light intensity (LL). FPLC-MS/MS allowed to reveal PucABd and PucBabc apoproteins in LL LH2 complex, which is different from previously described LH4 complex containing PucABd, PucABa and PucBb. The main carotenoids in LL LH2 complex were rhodopin and 3,4-didehydrorhodopin. Three-dimensional modeling demonstrated which amino acid residues of all the -subunits could interact with carotenoids (Car) and bacteriochlorophyll a (BChl a). Analysis of amino acid sequences of -subunits of both LL complexes showed presence of different C-terminal motifs, IESSVNVG in a subunit and IESSIKAV in d subunit, in the same positions of C-termini, which could reflect different retention force of LL LH2 and LH4 on hydroxyl apatite, facilitating successful isolation of these complexes. Differences of these LL complexes in protein and carotenoid composition, in efficiency of energy transfer from Car to BChl a, which is two times lower in LL LH2 than in LH4, allow to assign it to a novel type of light-harvesting complex in .
新型外周光捕获（LH）复合物被命名为 LL LH2，与在低光强（LL）下生长的细胞中的 LH4 复合物一起分离。FPLC-MS/MS 允许揭示 LL LH2 复合物中的 PucABd 和 PucBabc 脱辅基蛋白，这与先前描述的含有 PucABd、PucABa 和 PucBb 的 LH4 复合物不同。LL LH2 复合物中的主要类胡萝卜素是 rhodopin 和 3,4-二脱水 rhodopin。三维建模表明，所有 - 亚基的氨基酸残基都可以与类胡萝卜素（Car）和细菌叶绿素 a（BChl a）相互作用。对两种 LL 复合物的 - 亚基氨基酸序列分析表明，在同一 C 末端位置存在不同的 C 末端基序，a 亚基中的 IESSVNVG 和 d 亚基中的 IESSIKAV，这可能反映了 LL LH2 和 LH4 在羟基磷灰石上的不同保留力，有利于这些复合物的成功分离。这些 LL 复合物在蛋白质和类胡萝卜素组成、从 Car 到 BChl a 的能量转移效率方面存在差异，LL LH2 比 LH4 低两倍，这使其在 中被归为一种新型光捕获复合物。
