PDF(Pubmed)
Abstract：
Methylobacterium species, the representative bacteria distributed in phyllosphere region of plants, often synthesize carotenoids to resist harmful UV radiations. Methylobacterium extorquens is known to produce a carotenoid pigment and recent research revealed that this carotenoid has a C30 backbone. However, its exact structure remains unknown. In the present study, the carotenoid produced by M. extorquens AM1 was isolated and its structure was determined as 4-[2-O-11Z-octadecenoyl-β-glucopyranosyl]-4,4\'-diapolycopenedioc acid (1), a glycosylated C30 carotenoid. Furthermore, the genes related to the C30 carotenoid synthesis were investigated. Squalene, the precursor of the C30 carotenoid, is synthesized by the co-occurrence of META1p1815, META1p1816 and META1p1817. Further overexpression of the genes related to squalene synthesis improved the titer of carotenoid 1. By using gene deletion and gene complementation experiments, the glycosyltransferase META1p3663 and acyltransferase META1p3664 were firstly confirmed to catalyze the tailoring steps from 4,4\'-diapolycopene-4,4\'-dioic acid to carotenoid 1. In conclusion, the structure and biosynthetic genes of carotenoid 1 produced by M. extorquens AM1 were firstly characterized in this work, which shed lights on engineering M. extorquens AM1 for producing carotenoid 1 in high yield.
摘要：
甲基杆菌物种，代表细菌分布在植物的叶球区域，经常合成类胡萝卜素来抵抗有害的紫外线辐射。已知甲基杆菌会产生类胡萝卜素色素，最近的研究表明这种类胡萝卜素具有C30骨架。然而,它的确切结构仍然未知。在本研究中,分离了由M.extorquensAM1产生的类胡萝卜素，并确定其结构为4-[2-O-11Z-十八碳烯酰基-β-吡喃葡萄糖基]-4,4'-二聚二羧酸（1），一种糖基化的C30类胡萝卜素。此外，研究了与C30类胡萝卜素合成相关的基因。角鲨烯,C30类胡萝卜素的前体，由META1p1815、META1p1816和META1p1817共同出现而合成。角鲨烯合成相关基因的进一步过表达提高了类胡萝卜素1的效价。通过基因缺失和基因互补实验,首先确认了糖基转移酶META1p3663和酰基转移酶META1p3664催化了从4,4'-二聚-4,4'-二甲酸到类胡萝卜素1的定制步骤。总之,首先对M.extorquensAM1产生的类胡萝卜素1的结构和生物合成基因进行了表征,这为工程M.敲诈AM1以高产率生产类胡萝卜素1提供了启示。
