Horizontal-Acquisition of a Promiscuous Peptidoglycan-Recycling Enzyme Enables Aphids To Influence Symbiont Cell Wall Metabolism.
Horizontal-Acquisition of a Promiscuous Peptidoglycan-Recycling Enzyme Enables Aphids To Influence Symbiont Cell Wall Metabolism.
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DOI：
10.1128/mbio.02636-21
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发表时间：
2021-12-21
期刊：
影响因子：
6.4
通讯作者：
Moran NA
中科院分区：
文献类型：
--
作者：
Smith TE;Lee M;Person MD;Hesek D;Mobashery S;Moran NA
在进化过程中，酶的首选底物或催化活性可能会发生变化。一个有趣的问题是水平基因转移后酶功能如何变化，特别是对于已经转移到动物基因组的细菌基因。一些昆虫已经获得了编码用于细菌细胞壁成分生物合成的酶的基因，并且这些基因似乎具有支持或控制其专性内共生细菌的功能。在蚜虫中，细菌内共生体 Buchnera aphidicola 为蚜虫宿主提供必需氨基酸，但缺乏大多数用于重塑细菌细胞壁的基因。蚜虫基因组已经获得了七个在细胞壁代谢中具有推定功能的基因，这些基因主要在含有 Buchnera 的蚜虫细胞中表达。在对蚜虫匀浆的分析中，我们检测到了肽聚糖（PGN）壁肽，这些肽聚糖表明由水平获得的蚜虫基因而非Buchnera基因编码的PGN水解酶的反应。我们生产了一种这样的宿主酶 ApLdcA，并用细胞壁衍生的和合成的 PGN 来表征其活性。 ApLdcA 和大肠杆菌中的同源酶（在细胞质 PGN 回收途径中充当 L,D-羧肽酶）均表现出包含茎五肽的 PGN 底物的周转以及通过 L,D-内肽酶活性的交联，这与细胞壁重塑中的潜在作用一致。我们的结果表明，ApLdcA 的功能源自祖先 LdcA 酶的混杂活性，蚜虫基因组获得该酶可能使宿主能够影响 Buchnera 细胞壁代谢，作为控制共生体生长和分裂的手段。
During evolution, enzymes can undergo shifts in preferred substrates or in catalytic activities. An intriguing question is how enzyme function changes following horizontal gene transfer, especially for bacterial genes that have moved to animal genomes. Some insects have acquired genes that encode enzymes for the biosynthesis of bacterial cell wall components and that appear to function to support or control their obligate endosymbiotic bacteria. In aphids, the bacterial endosymbiont Buchnera aphidicola provides essential amino acids for aphid hosts but lacks most genes for remodeling of the bacterial cell wall. The aphid genome has acquired seven genes with putative functions in cell wall metabolism that are primarily expressed in the aphid cells harboring Buchnera. In analyses of aphid homogenates, we detected peptidoglycan (PGN) muropeptides indicative of the reactions of PGN hydrolases encoded by horizontally acquired aphid genes but not by Buchnera genes. We produced one such host enzyme, ApLdcA, and characterized its activity with both cell wall derived and synthetic PGN. Both ApLdcA and the homologous enzyme in Escherichia coli, which functions as an l,d-carboxypeptidase in the cytoplasmic PGN recycling pathway, exhibit turnover of PGN substrates containing stem pentapeptides and cross-linkages via l,d-endopeptidase activity, consistent with a potential role in cell wall remodeling. Our results suggest that ApLdcA derives its functions from the promiscuous activities of an ancestral LdcA enzyme, whose acquisition by the aphid genome may have enabled hosts to influence Buchnera cell wall metabolism as a means to control symbiont growth and division.