Department of Molecular Microbiology, John Innes Centre, Norwich, Norwich Research Park, NR4 7UH, UK.
Department Biochemistry and Metabolism, Proteomics Facility, John Innes Centre, Norwich, Norwich Research Park, NR4 7UH, UK.
Microbiology (Reading). 2023 Jul;169(7). doi: 10.1099/mic.0.001358.
CutRS was the first two-component system to be identified in species and is highly conserved in this genus. It was reported >25 years ago that deletion of increases the production of the antibiotic actinorhodin in . However, despite this early work, the function of CutRS has remained enigmatic until now. Here we show that deletion of upregulates the production of the actinorhodin biosynthetic enzymes up to 300-fold, explaining the increase in actinorhodin production. However, while ChIP-seq identified 85 CutR binding sites in none of these are in the actinorhodin biosynthetic gene cluster, meaning the effect is indirect. The directly regulated CutR targets identified in this study are implicated in extracellular protein folding, including two of the four highly conserved HtrA-family foldases: HtrA3 and HtrB, and a putative VKOR enzyme, which is predicted to recycle DsbA following its catalysis of disulphide bond formation in secreted proteins. Thus, we tentatively propose a role for CutRS in sensing and responding to protein misfolding outside the cell. Since actinorhodin can oxidise cysteine residues and induce disulphide bond formation in proteins, its over production in the mutant may be a response to protein misfolding on the extracellular face of the membrane.
CutRS 是第一个在 物种中被鉴定的双组份系统，在这个属中高度保守。早在 25 年前就有报道称， 的缺失会增加抗生素放线紫红素的产量。然而，尽管有这项早期的工作，CutRS 的功能至今仍是个谜。在这里，我们表明 的缺失会使放线紫红素生物合成酶的产量上调高达 300 倍，从而解释了放线紫红素产量增加的原因。然而，尽管 ChIP-seq 在 中鉴定了 85 个 CutR 结合位点，但这些结合位点都不在放线紫红素生物合成基因簇中，这意味着这种效应是间接的。本研究中鉴定的直接受 CutR 调控的靶标与细胞外蛋白质折叠有关，包括四个高度保守的 HtrA 家族折叠酶中的两个：HtrA3 和 HtrB，以及一个假定的 VKOR 酶，该酶在其催化分泌蛋白中二硫键形成后，预计会使 DsbA 循环利用。因此，我们推测 CutRS 在感知和响应细胞外蛋白质错误折叠方面发挥作用。由于放线紫红素可以氧化半胱氨酸残基并诱导蛋白质中二硫键的形成，因此在 突变体中过度产生可能是对膜外蛋白质错误折叠的一种反应。
