PR1A AND PR1G SUPPRESSORS REDUCE THE REQUIREMENT FOR SIGNAL SEQUENCE RECOGNITION
PR1A AND PR1G SUPPRESSORS REDUCE THE REQUIREMENT FOR SIGNAL SEQUENCE RECOGNITION
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DOI：
10.1128/jb.176.18.5607-5614.1994
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发表时间：
1994-09-01
影响因子：
3.2
通讯作者：
SILHAVY, TJ
中科院分区：
文献类型：
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作者：
FLOWER, AM;DOEBELE, RC;SILHAVY, TJ
分泌蛋白信号序列缺陷抑制子的选择最常导致prlA等位基因的鉴定，而不常导致prlG等位基因的鉴定。这些基因，secY/prlA和secE/prlG，编码大肠杆菌的蛋白质易位系统的整合膜组分。我们证明，外膜蛋白，LamB，缺乏信号序列，可以出口与合理的效率在prlA和prlG抑制菌株。虽然信号序列不是输出LamB所绝对需要的，但在不存在prl抑制等位基因的情况下，输出水平极低。这些菌株的表型为LamB（-），只有使用敏感的感染中心检测才能检测到功能性LamB。LamB信号序列缺失的抑制依赖于输出途径的正常组分，表明抑制不是通过旁路机制发生的。我们的研究结果表明，大多数已知的prlA抑制剂的功能相同的机制，并进一步，prlG抑制剂以类似的方式工作。我们认为PrlA和PrlG抑制子都缺乏通常拒绝出口途径中有缺陷的前体的校对活性。
Selection for suppressors of defects in the signal sequence of secretory proteins has led most commonly to identification of prlA alleles and less often to identification of prlG alleles. These genes, secY/prlA and secE/prlG, encode integral membrane components of the protein translocation system of Escherichia coli. We demonstrate that an outer membrane protein, LamB, that lacks a signal sequence can be exported with reasonable efficiency in both prlA and prlG suppressor strains. Although the signal sequence is not absolutely required for export of LamB, the level of export in the absence of prl suppressor alleles is exceedingly low. Such strains are phenotypically LamB(-), and functional LamB can be detected only by using sensitive infectious-center assays. Suppression of the LamB signal sequence deletion is dependent on normal components of the export pathway, indicating that suppression is not occurring through a bypass mechanism. Our results indicate that the majority of the known prlA suppressors function by an identical mechanism and, further, that the prlG suppressors work in a similar fashion. We propose that both PrlA and PrlG suppressors lack a proofreading activity that normally rejects defective precursors from the export pathway.