Lipid membrane mimetics and oligomerization tune functional properties of proteorhodopsin
Lipid membrane mimetics and oligomerization tune functional properties of proteorhodopsin
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脂质膜模拟物和寡聚调节蛋白视紫红质的功能特性
DOI：
10.1016/j.bpj.2022.11.012
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发表时间：
2022
影响因子：
3.4
通讯作者：
Aye, Emily
中科院分区：
文献类型：
--
作者：
Han, Chung-Ta;Nguyen, Khanh Dinh;Berkow, Maxwell W.;Hussain, Sunyia;Kiani, Ahmad;Kinnebrew, Maia;Idso, Matthew N.;Baxter, Naomi;Chang, Evelyn;Aye, Emily
蛋白紫质（PR）的功能特性已被发现受到寡聚分布和脂质膜模拟物的强烈调节。本研究旨在通过研究低聚物的形成如何影响PR在脂基膜模拟环境中的质子运输功能来区分和解释它们的作用。我们发现PR在两者中形成稳定的六聚体和五聚体。共膜和合成脂质体。与单体相比，PR低聚体的光循环动力学在kandand mandn光中间体之间的转换分别慢了~ 2和~ 4.5倍，这表明寡聚化显著减缓了PR在脂质体中质子运输的速度。相比之下，脂质体包埋PR的关键质子受体残基D97 （pKaD97）的表观pKa维持在6.2-6.6，无论D97是否被交叉原聚体调节，这表明脂质体环境有助于在中性ph下维持PR的功能活性。相比之下，当直接从me中提取时。富含单体的E50Q PR的pkad97急剧增加至8.9，表明在中性pH下，参与PR光循环的活性PR群体非常低。这些发现表明，寡聚化影响PR的光循环动力学，而基于脂质的膜模拟物通过不同的机制强烈影响PR的活性种群。
The functional properties of proteorhodopsin (PR) have been found to be strongly modulated by oligomeric distributions and lipid membrane mimetics. This study aims to distinguish and explain their effects by investigating how oligomer formation impacts PR's function of proton transport in lipid-based membrane mimetic environments. We find that PR forms stable hexamers and pentamers in bothE. colimembranes and synthetic liposomes. Compared with the monomers, the photocycle kinetics of PR oligomers is ∼2 and ∼4.5 times slower for transitions between theKandMand theMandNphotointermediates, respectively, indicating that oligomerization significantly slows PR's rate of proton transport in liposomes. In contrast, the apparent pKa of the key proton acceptor residue D97 (pKaD97) of liposome-embedded PR persists at 6.2–6.6, regardless of cross-protomer modulation of D97, suggesting that the liposome environment helps maintain PR's functional activity at neutral pH. By comparison, when extracted directly fromE. colimembranes into styrene-maleic acid lipid particles, the pKaD97of monomer-enriched E50Q PR drastically increases to 8.9, implying that there is a very low active PR population at neutral pH to engage in PR's photocycle. These findings demonstrate that oligomerization impacts PR's photocycle kinetics, while lipid-based membrane mimetics strongly affect PR's active population via different mechanisms.