Hydrophilicity of a single residue within MscL correlates with increased channel mechanosensitivity
Hydrophilicity of a single residue within MscL correlates with increased channel mechanosensitivity
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DOI：
10.1016/s0006-3495(99)77037-2
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发表时间：
1999-10-01
影响因子：
3.4
通讯作者：
Kung, C
中科院分区：
文献类型：
--
作者：
Yoshimura, K;Batiza, A;Kung, C
机械敏感通道大分子(MSCL)编码大肠杆菌内膜的大电导机械敏感通道，保护细菌免受渗透休克的溶解。为了阐明MSCL门控的分子机制，我们用所有其他常见的氨基酸全面取代了Gly(22)。Gly(22)在E.coliMSCL的随机突变筛选中被突出显示(ou等人，1998，Proc.纳特。阿卡德。SCI。美国。95：11471-11475)。通过类比最近发表的来自结核分枝杆菌的MSCL结构(Chang等人，1998，《科学》。282：2220-2226)，Gly(22)被埋在关闭毛孔的狭窄处。用亲水性残基取代甘氨酸(22)降低了通道打开的阈值压力，并揭示了中间亚导电状态。相反，疏水取代增加了阈值压力。尽管疏水取代对生长没有影响，类似于MSCL缺失的影响，但亲水取代引起的通道过度活跃与增殖减少相关。这些结果提出了一种门控模型，在该模型中，Gly(22)从疏水的环境中移动，并在从封闭构象转变为开放构象时通过亲水环境。
Mechanosensitive channel large (MscL) encodes the large conductance mechanosensitive channel of the Escherichia coli inner membrane that protects bacteria from lysis upon osmotic shock. To elucidate the molecular mechanism of MscL gating, we have comprehensively substituted Gly(22) with all other common amino acids. Gly(22) was highlighted in random mutagenesis screens of E. coli MscL (Ou et al., 1998, Proc. Nat. Acad. Sci. USA. 95:11471-11475). By analogy to the recently published MscL structure from Mycobacterium tuberculosis (Chang et al., 1998, Science. 282:2220-2226), Gly(22) is buried within the constriction that closes the pore. Substituting Gly(22) With hydrophilic residues decreased the threshold pressure at which channels opened and uncovered an intermediate subconducting state. In contrast, hydrophobic substitutions increased the threshold pressure. Although hydrophobic substitutions had no effect on growth, similar to the effect of an MscL deletion, channel hyperactivity caused by hydrophilic substitutions corrrelated with decreased proliferation. These results suggest a model for gating in which Gly(22) moves from a hydrophobic, and through a hydrophilic, environmment upon transition from the closed to open conformation.