Department of Animal Biology, School of Life Sciences, University of Hyderabad, Hyderabad, India.
National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Campus, Bengaluru, India.
Appl Environ Microbiol. 2023 May 31;89(5):e0190322. doi: 10.1128/aem.01903-22. Epub 2023 Apr 19.
Organophosphate hydrolases (OPH), hitherto known to hydrolyze the third ester bond of organophosphate (OP) insecticides and nerve agents, have recently been shown to interact with outer membrane transport components, namely, TonB and ExbB/ExbD. In an OPH negative background, Sphingopyxis wildii cells failed to transport ferric enterobactin and showed retarded growth under iron-limiting conditions. We now show the OPH-encoding organophosphate degradation () gene from Sphingobium fuliginis ATCC 27551 to be part of the iron regulon. A -box motif found to be overlapping with the transcription start site (TSS) of the gene coordinates with an iron responsive element (IRE) RNA motif identified in the 5' coding region of the mRNA to tightly regulate gene expression. The -box motif serves as a target for the Fur repressor in the presence of iron. A decrease in iron concentration leads to the derepression of . IRE RNA inhibits the translation of mRNA and serves as a target for apo-aconitase (IRP). The IRP recruited by the IRE RNA abrogates IRE-mediated translational inhibition. Our findings establish a novel, multilayered, iron-responsive regulation that is crucial for OPH function in the transport of siderophore-mediated iron uptake. Sphingobium fuliginis, a soil-dwelling microbe isolated from agricultural soils, was shown to degrade a variety of insecticides and pesticides. These synthetic chemicals function as potent neurotoxins, and they belong to a class of chemicals termed organophosphates. codes for OPH, an enzyme that has been shown to be involved in the metabolism of several organophosphates and their derivatives. Interestingly, OPH has also been shown to facilitate siderophore-mediated iron uptake in and in another Sphingomonad, namely, , implying that this organophosphate-metabolizing protein has a role in iron homeostasis, as well. Our research dissects the underlying molecular mechanisms linking iron to the expression of OPH, prompting a reconsideration of the role of OPH in Sphingomonads and a reevaluation of the evolutionary origins of the OPH proteins from soil bacteria.
有机磷水解酶（OPH），迄今为止已知其能水解有机磷（OP）杀虫剂和神经毒剂的第三个酯键，最近已被证明与外膜转运成分相互作用，即 TonB 和 ExbB/ExbD。在 OPH 阴性背景下，Sphingopyxis wildii 细胞无法转运铁载体 enterobactin，并在缺铁条件下生长缓慢。我们现在表明，来自 Sphingobium fuliginis ATCC 27551 的 OPH 编码有机磷降解基因是铁调节子的一部分。在 基因的转录起始位点（TSS）上发现的一个 B 盒基序与在 mRNA 的 5'编码区中鉴定的铁反应元件（IRE）RNA 基序重叠，以紧密调节 基因表达。在存在铁的情况下，B 盒基序作为 Fur 阻遏物的靶标。铁浓度的降低导致 的去阻遏。IRE RNA 抑制 mRNA 的翻译，并作为脱辅基 aconitase（IRP）的靶标。IRE RNA 招募的 IRP 消除了 IRE 介导的翻译抑制。我们的发现建立了一种新的、多层次的、铁反应性调节，这对于 OPH 在铁载体介导的铁摄取运输中的功能至关重要。 Sphingobium fuliginis 是一种从农业土壤中分离出来的土壤微生物，已被证明能够降解多种杀虫剂和农药。这些合成化学品是有效的神经毒素，它们属于一类称为有机磷的化学物质。 编码 OPH，一种已被证明参与几种有机磷及其衍生物代谢的酶。有趣的是，OPH 还被证明有助于 和另一种 Sphingomonad，即 中的铁载体介导的铁摄取，这意味着这种有机磷代谢蛋白在铁稳态中也具有作用。我们的研究剖析了将铁与 OPH 表达联系起来的潜在分子机制，促使人们重新考虑 OPH 在 Sphingomonads 中的作用，并重新评估来自土壤细菌的 OPH 蛋白的进化起源。
