Characterization of the role of the divalent metal ion-dependent transcriptional repressor MntR in the virulence of Staphylococcus aureus
Characterization of the role of the divalent metal ion-dependent transcriptional repressor MntR in the virulence of Staphylococcus aureus
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DOI：
10.1128/iai.71.5.2584-2590.2003
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发表时间：
2003-05-01
影响因子：
3.1
通讯作者：
Bishai, WR
中科院分区：
文献类型：
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作者：
Ando, M;Manabe, YC;Bishai, WR
dtxr型金属离子依赖性抑制因子存在于许多细菌病原体中，可能调节诸如编码白喉毒素的毒力基因的表达。SirR是最初在表皮葡萄球菌中发现的DtxR同源物，控制邻近的sitABC操纵子的表达，该操纵子编码一个假定的金属离子ABC转运系统。我们在金黄色葡萄球菌中发现了sirR的同源物mntR，并通过凝胶移位实验证明，在Fe2+或Mn2+存在下，棒状细菌抑制因子DtxR与金黄色葡萄球菌mntABC操作符结合。由于DtxR突变体DtxR（E175K）在某些情况下作为铁非依赖性高阻遏因子发挥作用，我们构建了一株从天然mntR启动子表达DtxR（E175K）的异二倍体金黄色葡萄球菌菌株。在野生型和异二倍体金黄色葡萄球菌菌株中，Fe2+或Mn2+的存在抑制了金黄色葡萄球菌mntABC操纵子的转录。在金属离子限制条件下，与等基因对照相比，表达dtxR（E175K）的金黄色葡萄球菌分离株的mntABC转录减少，但未完全消除，这表明dtxR（E175K）在体内与金黄色葡萄球菌MntR盒子结合。在所有测试条件下，与等基因对照相比，表达dtxR（E175K）的菌株的mntABC转录减少，表明dtxR（E175K）功能具有组成性活性。在小鼠皮肤脓肿模型中，与等基因野生型对照相比，表达dtxR（E175K）的金黄色葡萄球菌重组体的CFU水平显著降低。我们得出结论，金黄色葡萄球菌MntR盒子被杆状细菌DtxR蛋白识别，因此属于DtxR金属依赖性操作位点家族。此外，DtxR（E175K）的本构抑制可降低金黄色葡萄球菌对小鼠皮肤脓肿模型的毒力。
DtxR-type metal ion-dependent repressors, present in many bacterial pathogens, may regulate expression of virulence genes such as that encoding diphtheria toxin. SirR, a DtxR homologue initially identified in Staphylococcus epidermidis, governs the expression of the adjacent sitABC operon encoding a putative metal ion ABC transporter system. We identified a sirR homologue, mntR, in Staphylococcus aureus and demonstrated by gel shift assay that the corynebacterial repressor DtxR binds to the S. aureus mntABC operator in the presence of Fe2+ or Mn2+. Since a mutant DtxR, DtxR(E175K), functions as an iron-independent hyperrepressor in certain settings, we constructed a heterodiploid S. aureus strain expressing dtxR(E175K) from the native mntR promoter. Transcription of the S. aureus mntABC operon was repressed in the presence of Fe2+ or Mn2+ in wild-type and heterodiploid S. aureus strains. Under metal ion-limiting conditions, mntABC transcription was reduced but not abolished in S. aureus isolates expressing dtxR(E175K) compared with an isogenic control, suggesting that DtxR(E175K) binds the S. aureus MntR box in vivo. Under all conditions tested, mntABC transcription in the dtxR(E175K)-expressing strain was reduced relative to the isogenic control, indicating that DtxR(E175K) function was constitutively active. In the mouse skin abscess model, dtxR(E175K)-expressing S. aureus recombinants showed significantly reduced CFU levels compared with the isogenic wild-type control. We conclude that the S. aureus MntR box is recognized by corynebacterial DtxR proteins and thus belongs to the DtxR family of metal-dependent operator sites. Moreover, constitutive repression by DtxR(E175K) reduces the virulence of S. aureus in the mouse skin abscess model.