Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, USA.
Department of Biochemistry and Biophysics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
Acta Crystallogr D Struct Biol. 2021 Aug 1;77(Pt 8):1027-1039. doi: 10.1107/S2059798321006288. Epub 2021 Jul 29.
Vancomycin has historically been used as a last-resort treatment for serious bacterial infections. However, vancomycin resistance has become widespread in certain pathogens, presenting a serious threat to public health. Resistance to vancomycin is conferred by a suite of resistance genes, the expression of which is controlled by the VanR-VanS two-component system. VanR is the response regulator in this system; in the presence of vancomycin, VanR accepts a phosphoryl group from VanS, thereby activating VanR as a transcription factor and inducing expression of the resistance genes. This paper presents the X-ray crystal structures of full-length VanR from Streptomyces coelicolor in both the inactive and activated states at resolutions of 2.3 and 2.0 Å, respectively. Comparison of the two structures illustrates that phosphorylation of VanR is accompanied by a disorder-to-order transition of helix 4, which lies within the receiver domain of the protein. This transition generates an interface that promotes dimerization of the receiver domain; dimerization in solution was verified using analytical ultracentrifugation. The inactive conformation of the protein does not appear intrinsically unable to bind DNA; rather, it is proposed that in the activated form DNA binding is enhanced by an avidity effect contributed by the receiver-domain dimerization.
万古霉素在历史上一直被用作治疗严重细菌感染的最后手段。然而，万古霉素耐药性在某些病原体中已经广泛存在，这对公共卫生构成了严重威胁。万古霉素耐药性是由一系列耐药基因赋予的，这些基因的表达受 VanR-VanS 二组分系统的控制。VanR 是该系统中的响应调节剂；在万古霉素存在的情况下，VanR 从 VanS 接受一个磷酸基团，从而激活 VanR 作为转录因子，并诱导耐药基因的表达。本文介绍了来自变铅青链霉菌全长 VanR 的 X 射线晶体结构，在 2.3 和 2.0 Å 的分辨率下分别处于非活性和激活状态。对这两个结构的比较表明，VanR 的磷酸化伴随着螺旋 4 的无序到有序的转变，该螺旋位于该蛋白的受体结构域内。这种转变产生了一个促进受体结构域二聚化的界面；使用分析超速离心法验证了溶液中二聚体的形成。该蛋白的非活性构象似乎并不是内在地不能结合 DNA；而是提出在激活形式下，DNA 结合通过受体结构域二聚化的亲和力效应得到增强。
