ΔμH⁺和ATP在前体蛋白转位酶催化循环的不同步骤中发挥作用。
Delta mu H+ and ATP function at different steps of the catalytic cycle of preprotein translocase.
作者信息
Schiebel E, Driessen A J, Hartl F U, Wickner W
机构信息
Molecular Biology Institute, University of California, Los Angeles 90024-15.
出版信息
Cell. 1991 Mar 8;64(5):927-39. doi: 10.1016/0092-8674(91)90317-r.
Preprotein translocation in E. coli requires ATP, the membrane electrochemical potential delta mu H+, and translocase, an enzyme with an ATPase domain (SecA) and the membrane-embedded SecY/E. Studies of translocase and proOmpA binds to the SecA domain. Second, SecA binds ATP. Third, ATP-binding energy permits translocation of approximately 20 residues of proOmpA. Fourth, ATP hydrolysis releases proOmpA. ProOmpA may then rebind to SecA and reenter this cycle, allowing progress through a series of transmembrane intermediates. In the absence of delta mu H+ or association with SecA, proOmpA passes backward through the membrane, but moves forward when either ATP and SecA or a membrane electrochemical potential is supplied. However, in the presence of delta mu H+ (fifth step), proOmpA rapidly completes translocation. delta mu H(+)-driven translocation is blocked by SecA plus nonhydrolyzable ATP analogs, indicating that delta mu H+ drives translocation when ATP and proOmpA are not bound to SecA.
大肠杆菌中的前体蛋白转运需要ATP、膜电化学势ΔμH⁺以及转运酶，转运酶是一种具有ATP酶结构域（SecA）和嵌入膜中的SecY/E的酶。对转运酶的研究表明，前体OmpA与SecA结构域结合。第二，SecA结合ATP。第三，ATP结合能允许前体OmpA约20个残基的转运。第四，ATP水解释放前体OmpA。然后前体OmpA可能重新结合到SecA并重新进入这个循环，从而通过一系列跨膜中间体取得进展。在没有ΔμH⁺或与SecA结合的情况下，前体OmpA会逆向穿过膜，但当提供ATP和SecA或膜电化学势时会向前移动。然而，在存在ΔμH⁺（第五步）的情况下，前体OmpA会迅速完成转运。由ΔμH⁺驱动的转运被SecA加不可水解的ATP类似物阻断，这表明当ATP和前体OmpA未与SecA结合时，ΔμH⁺驱动转运。
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