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首页> 外文期刊>Journal of bacteriology >Identification of a Lycopene β-Cyclase Required for Bacteriorhodopsin Biogenesis in the Archaeon Halobacterium salinarum
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Identification of a Lycopene β-Cyclase Required for Bacteriorhodopsin Biogenesis in the Archaeon Halobacterium salinarum

机译：细菌古细菌盐藻中细菌视紫红质生物发生所需的番茄红素β-环化酶的鉴定

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Biogenesis of the light-driven proton pump bacteriorhodopsin in the archaeon Halobacterium salinarum requires coordinate synthesis of the bacterioopsin apoprotein and carotenoid precursors of retinal, which serves as a covalently bound cofactor. As a step towards elucidating the mechanism and regulation of carotenoid metabolism during bacteriorhodopsin biogenesis, we have identified an H. salinarum gene required for conversion of lycopene to β-carotene, a retinal precursor. The gene, designated crtY, is predicted to encode an integral membrane protein homologous to lycopene β-cyclases identified in bacteria and fungi. To test crtY function, we constructed H. salinarum strains with in-frame deletions in the gene. In the deletion strains, bacteriorhodopsin, retinal, and β-carotene were undetectable, whereas lycopene accumulated to high levels (≈1.3 nmol/mg of total cell protein). Heterologous expression of H. salinarum crtY in a lycopene-producing Escherichia coli strain resulted in β-carotene production. These results indicate that H. salinarum crtY encodes a functional lycopene β-cyclase required for bacteriorhodopsin biogenesis. Comparative sequence analysis yields a topological model of the protein and provides a plausible evolutionary connection between heterodimeric lycopene cyclases in bacteria and bifunctional lycopene cyclase-phytoene synthases in fungi.
机译：在古细菌盐藻中光驱动质子泵细菌视紫红质的生物发生需要视网膜视球菌的脱辅基蛋白和类胡萝卜素前体的协调合成，后者是共价结合的辅因子。为了阐明细菌视紫红质生物发生过程中类胡萝卜素代谢的机制和调控的一步，我们确定了 H。番茄红素转化为视网膜前体β-胡萝卜素所需的盐基因。据预测，该基因称为“ crtY ”，其编码的完整膜蛋白与细菌和真菌中鉴定出的番茄红素β-环化酶同源。为了测试 crtY 函数，我们构造了 H。该基因中框内缺失的盐沼菌株。在缺失菌株中，细菌视紫红质，视网膜和β-胡萝卜素是无法检测到的，而番茄红素的积累水平很高（≈1.3nmol / mg总细胞蛋白）。 H的异源表达。产番茄红素的大肠杆菌中的salinarum crtY 导致β-胡萝卜素的产生。这些结果表明 H。 salinarum crtY 编码细菌视紫红质生物发生所需的功能性番茄红素β-环化酶。比较序列分析产生了该蛋白质的拓扑模型，并提供了细菌中异二聚番茄红素环化酶与真菌中双功能番茄红素环化酶-并四氢番茄红素合酶之间合理的进化联系。

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