Department of Chemical Engineering, University of Washington, Seattle, WA, USA.
Mol Microbiol. 2019 May;111(5):1127-1131. doi: 10.1111/mmi.14210. Epub 2019 Mar 28.
Recently, rare-earth elements lanthanides (Ln ) have emerged as enzyme cofactors of methanol dehydrogenases of the XoxF type. It is now understood that XoxF enzymes can functionally replace the alternative, calcium-dependent, MxaFI-type methanol dehydrogenases, when Ln are available. These rare-earth metals are not only essential for XoxF activity, but they also regulate gene expression, in a reverse fashion, activating the expression of XoxF and repressing the expression of MxaFI. This type of regulation has created multiple conundrums, including the details of the solubility, transport, sensing and selection mechanisms for Ln by the bacterial cells, as well as the questions relevant to the evolution of the alternative enzymes and their potentially different redox properties. Overall, the newly discovered biological activity of Ln presents a big puzzle. Ochsner et al. add several pieces to this puzzle, utilizing a model phyllosphere colonizer Methylobacterium extorquens PA1. They determine that Ln sensing by this organism can take place via both XoxF-dependent and XoxF-independent mechanisms. They also identify genes for a TonB-dependent transporter and an ABC-type transporter and demonstrate that both are essential for Ln -dependent methanol metabolism. The puzzle still requires multiple additional pieces for completion, but great strides have been made toward the goal of solving it.
最近，稀土元素镧系元素 (Ln) 已成为 XoxF 型甲醇脱氢酶的酶辅因子。现在人们已经了解到，当有 Ln 存在时，XoxF 酶可以替代替代的、依赖钙的 MxaFI 型甲醇脱氢酶发挥功能。这些稀土金属不仅对 XoxF 活性至关重要，而且它们还以相反的方式调节基因表达，激活 XoxF 的表达并抑制 MxaFI 的表达。这种调节类型造成了多个难题，包括细菌细胞对 Ln 的可溶性、运输、感应和选择机制的细节，以及与替代酶的进化及其潜在不同氧化还原性质相关的问题。总的来说，Ln 的新发现的生物活性提出了一个大难题。Ochsner 等人为此难题增添了几个部分，他们利用模式叶际定殖者甲基杆菌 PA1 作为模型。他们确定，该生物体对 Ln 的感应可以通过 XoxF 依赖和 XoxF 独立的机制发生。他们还鉴定了 TonB 依赖性转运蛋白和 ABC 型转运蛋白的基因，并证明这两种蛋白对 Ln 依赖的甲醇代谢都是必需的。要完成这个难题还需要多个其他部分，但在解决这个难题的目标方面已经取得了重大进展。
