Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, New York, USA.
Department of Microbiology, NYU Langone Medical Center, New York, New York, USA.
J Bacteriol. 2018 Feb 7;200(5). doi: 10.1128/JB.00611-17. Print 2018 Mar 1.
has three types of cation/proton antiporters. The type 3 family includes two ultisubunit a/ (Mnh) antiporters, Mnh1 and Mnh2. These antiporters are clusters of seven hydrophobic membrane-bound protein subunits. Mnh antiporters play important roles in maintaining cytoplasmic pH in prokaryotes, enabling their survival under extreme environmental stress. In this study, we investigated the physiological roles and catalytic properties of Mnh1 and Mnh2 in Both Mnh1 and Mnh2 were cloned separately into a pGEM3Z+ vector in the antiporter-deficient KNabc strain. The catalytic properties of the antiporters were measured in everted (inside out) vesicles. The Mnh1 antiporter exhibited a significant exchange of Na/H cations at pH 7.5. Mnh2 showed a significant exchange of both Na/H and K/H cations, especially at pH 8.5. Under elevated salt conditions, deletion of the gene resulted in a significant reduction in the growth rate of in the range of pH 7.5 to 9. Deletion of had similar effects but mainly in the range of pH 8.5 to 9.5. Double deletion of and led to a severe reduction in the growth rate mainly at pH values above 8.5. The effects of functional losses of both antiporters in were also assessed via their support of virulence in a mouse infection model. Deletion of the gene led to a major loss of virulence in mice, while deletion of led to no change in virulence. This study focuses on the catalytic properties and physiological roles of Mnh1 and Mnh2 cation/proton antiporters in and their contributions under different stress conditions. The Mnh1 antiporter was found to have catalytic activity for Na/H antiport, and it plays a significant role in maintaining halotolerance at pH 7.5 while the Mnh2 antiporter has catalytic antiporter activities for Na/H and K/H that have roles in both osmotolerance and halotolerance in Study of with a single deletion of either or was assessed in an infection model of mice. The result shows that , but not , plays a major role in virulence.
该蛋白家族包括两个多亚基 a/（Mnh）反向转运体，Mnh1 和 Mnh2。这些转运体是由七个疏水性跨膜蛋白亚基组成的簇。Mnh 反向转运体在原核生物中发挥着重要作用，使它们能够在极端环境压力下生存。在这项研究中，我们研究了 Mnh1 和 Mnh2 在嗜盐古菌中的生理作用和催化特性。分别将 Mnh1 和 Mnh2 克隆到反向转运体缺陷型 KNabc 菌株的 pGEM3Z+载体中。在外翻小体中测量转运体的催化特性。在 pH7.5 时，Mnh1 反向转运体表现出显著的 Na+/H+阳离子交换。Mnh2 显示出显著的 Na+/H+和 K+/H+阳离子交换，特别是在 pH8.5 时。在高盐条件下，缺失 基因导致 在 pH7.5 到 9 的范围内生长速率显著降低。缺失 基因也有类似的影响，但主要在 pH8.5 到 9.5 的范围内。同时缺失 和 基因导致 在 pH 值高于 8.5 时生长速率严重降低。通过在小鼠感染模型中评估其对毒力的支持，还评估了 在缺失这两种反向转运体后的功能丧失的影响。缺失 基因导致 在小鼠中的毒力显著降低，而缺失 基因则不改变毒力。本研究重点研究了 Mnh1 和 Mnh2 阳离子/质子反向转运体在嗜盐古菌中的催化特性和生理作用及其在不同应激条件下的作用。发现 Mnh1 反向转运体具有 Na+/H+反向转运的催化活性，在 pH7.5 时对维持耐盐性有重要作用，而 Mnh2 反向转运体具有 Na+/H+和 K+/H+的催化活性，在嗜盐古菌的耐渗透压和耐盐性中均发挥作用。研究了在单个缺失 或 时的嗜盐古菌在小鼠感染模型中的作用。结果表明， 而不是 ，在嗜盐古菌的毒力中起主要作用。
