Biochemical evidence for the secY24 defect in Escherichia coli protein translocation and its suppression by soluble cytoplasmic factors.
Biochemical evidence for the secY24 defect in Escherichia coli protein translocation and its suppression by soluble cytoplasmic factors.
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大肠杆菌蛋白易位中 secY24 缺陷及其受可溶性细胞质因子抑制的生化证据。
DOI：
10.1073/pnas.84.21.7448
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发表时间：
1987
影响因子：
11.1
通讯作者：
Tai,PC
中科院分区：
文献类型：
--
作者：
Fandl,JP;Tai,PC
secY （prlA）基因产物是一种完整的膜蛋白，已被遗传学鉴定为大肠杆菌蛋白易位机制的核心成分之一。我们研究了secY24（温度敏感）突变对大肠杆菌倒膜囊泡蛋白易位活性的影响。从携带该等位基因的细胞中分离出的囊泡，在非允许温度（42℃）下生长，其易位活性低于在相同条件下从等基因secY+菌株中分离出的囊泡的1%。在允许温度（32℃）下生长的突变菌株的囊泡具有部分活性，但在40℃下预孵育的囊泡失去了90%的活性。此外，来自野生型细胞或生长在不允许温度下的secY24细胞的S300可溶性组分抑制或补偿了体内或体外灭活囊泡上的secY24易位缺陷。该抑制因子热不稳定且对蛋白酶k敏感。这些结果为SecY在易位过程中的重要作用提供了生化证据，并表明SecY24膜的易位缺陷可以通过补充额外的可溶性细胞质蛋白来补偿。
The secY (prlA) gene product is an integral membrane protein that has been identified genetically as one of the central components of the Escherichia coli protein translocation machinery. We have examined the effect of the secY24 (temperature-sensitive) mutation on the protein translocation activity of E. coli inverted membrane vesicles. Vesicles isolated from cells carrying this allele and grown at the nonpermissive temperature (42 degrees C) were less than 1% as active in translocation as vesicles isolated from an isogenic secY+ strain under the same conditions. Vesicles from the mutant strain grown at the permissive temperature (32 degrees C) were partially active, but those vesicles preincubated at 40 degrees C lost 90% of their activity. Moreover, the secY24 translocation defect on in vivo- or in vitro-inactivated vesicles was suppressed, or compensated, by an S300 soluble fraction from wild-type cells or from secY24 cells grown at nonpermissive temperature. The suppressing factor(s) was heat-labile and sensitive to proteinase K. These results provide biochemical evidence for the essential role of SecY in the translocation process and indicate that the translocation defect of SecY24 membranes can be compensated for by supplementing with additional soluble cytoplasmic proteins.