Histidine residues are involved in translocation-coupled ATP hydrolysis by the Sec-A protein.
Histidine residues are involved in translocation-coupled ATP hydrolysis by the Sec-A protein.
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组氨酸残基参与 Sec-A 蛋白的易位偶联 ATP 水解。
DOI：
10.1006/bbrc.1993.2201
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发表时间：
1993
影响因子：
3.1
通讯作者：
S. Mizushima
中科院分区：
文献类型：
--
作者：
H. Tokuda;M. Yamanaka;S. Mizushima
SecA是大肠杆菌蛋白质易位机制的重要组成部分，用组氨酸特异性试剂焦碳酸二乙基处理后，其易位偶联atp酶（易位atp酶）活性显著降低，这需要分泌前蛋白和膜囊泡，而其内源性atp酶（SecA- atp酶）活性提高了2倍。由于n -碳氧基组氨酸的形成，焦碳酸二乙酯处理的SecA在240 nm处表现出最大的吸收。对SecA分子中22个组氨酸残基中的5个进行修饰后，其易位ATPase活性降低，SecA-ATPase活性增强。完整的和修饰的SecA对ATP、proOmpA和细胞膜的亲和力相似，而易位ATP酶活性的Vmax明显低于修饰的SecA。ATP对SecA的修饰无影响。综上所述，这些结果表明，对焦碳酸二乙酯敏感的组氨酸残基是易位ATP酶所必需的，但不直接参与ATP、proOmpA和膜的结合。讨论了易位atp酶取消的可能原因。
Treatment of SecA, an essential component of the protein translocation machinery of Escherichia coli, with a histidine-specific reagent, diethylpyrocarbonate, caused significant abolition of its translocation-coupled ATPase (translocation ATPase) activity, which requires a presecretory protein and membrane vesicles, whereas its endogenous ATPase (SecA-ATPase) activity was enhanced by a factor of 2. Diethylpyrocarbonate-treated SecA exhibited an absorption maximum at 240 nm due to the formation of N-carbethoxyhistidine. Upon the modification of about 5 of the total 22 histidine residues in the SecA molecule, both the abolition of its translocation ATPase activity and the enhancement of its SecA-ATPase activity occurred. Intact and modified SecA exhibited similar affinities for ATP, proOmpA and membranes, whereas Vmax of the translocation ATPase activity was significantly lower in the case of the modified SecA. ATP had no effect on the modification of SecA. Taken together, these results indicate that histidine residues susceptible to diethylpyrocarbonate are essential for the translocation ATPase, but not directly involved in the binding of ATP, proOmpA and membranes. A possible reason for the abolition of translocation ATPase is discussed.