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一种非典型的黑色素生物合成途径可保护土曲霉分生孢子抵御环境胁迫。

A Non-canonical Melanin Biosynthesis Pathway Protects Aspergillus terreus Conidia from Environmental Stress.

机构信息

Microbial Biochemistry and Physiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knoell Institute, Beutenbergstr. 11a, 07745 Jena, Germany; Fungal Genetics and Biology Group, School of Life Sciences, University of Nottingham, University Park, Nottingham NG7 2RD, UK.

Microbial Biochemistry and Physiology, Leibniz Institute for Natural Product Research and Infection Biology, Hans Knoell Institute, Beutenbergstr. 11a, 07745 Jena, Germany.

出版信息

Cell Chem Biol. 2016 May 19;23(5):587-597. doi: 10.1016/j.chembiol.2016.03.014. Epub 2016 Apr 28.

Abstract

Melanins are ubiquitous pigments found in all kingdoms of life. Most organisms use them for protection from environmental stress, although some fungi employ melanins as virulence determinants. The human pathogenic fungus Aspergillus fumigatus and related Ascomycetes produce dihydroxynaphthalene- (DHN) melanin in their spores, the conidia, and use it to inhibit phagolysosome acidification. However, biosynthetic origin of melanin in a related fungus, Aspergillus terreus, has remained a mystery because A. terreus lacks genes for synthesis of DHN-melanin. Here we identify genes coding for an unusual NRPS-like enzyme (MelA) and a tyrosinase (TyrP) that A. terreus expressed under conidiation conditions. We demonstrate that MelA produces aspulvinone E, which is activated for polymerization by TyrP. Functional studies reveal that this new pigment, Asp-melanin, confers resistance against UV light and hampers phagocytosis by soil amoeba. Unexpectedly, Asp-melanin does not inhibit acidification of phagolysosomes, thus likely contributing specifically to survival of A. terreus conidia in acidic environments.

摘要

黑色素是存在于所有生命领域的普遍色素。大多数生物体用它们来抵御环境压力,尽管有些真菌将黑色素用作毒力决定因素。人类致病真菌烟曲霉和相关的子囊菌在其孢子(分生孢子)中产生二羟基萘醌(DHN)黑色素,并利用它来抑制吞噬体酸化。然而,相关真菌土曲霉中黑色素的生物合成来源仍然是一个谜,因为土曲霉缺乏合成 DHN-黑色素的基因。在这里,我们鉴定了编码一种不寻常的 NRPS 样酶(MelA)和酪氨酸酶(TyrP)的基因,这些基因在分生孢子形成条件下被 A. terreus 表达。我们证明 MelA 产生了 aspulvinone E,它被 TyrP 激活用于聚合。功能研究表明,这种新的色素,Asp-黑色素,赋予了对紫外线的抗性,并阻碍了土壤变形虫的吞噬作用。出乎意料的是,Asp-黑色素并不抑制吞噬体溶酶体的酸化,因此可能专门有助于土曲霉分生孢子在酸性环境中的存活。

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