Membrane insertion of the F-pilin subunit is Sec independent but requires leader peptidase B and the proton motive force.
Membrane insertion of the F-pilin subunit is Sec independent but requires leader peptidase B and the proton motive force.
复制标题
F-pilin 亚基的膜插入与 Sec 无关，但需要前导肽酶 B 和质子动力。
DOI：
10.1128/jb.178.13.3742-3747.1996
复制
发表时间：
1996
影响因子：
3.2
通讯作者：
Ippen-Ihler,K
中科院分区：
文献类型：
--
作者：
Majdalani,N;Ippen-Ihler,K
F菌毛蛋白是携带F质粒的大肠杆菌的接合菌毛在细胞表面组装所需的亚基。F-pilin前体proproin的成熟涉及三个F质粒转移产物：TraA， proproin前体；TraQ，促进高效proproin处理；以及7-kDa肽肽氨基末端乙酰化所需的TraX。成熟的毛蛋白开始于TraA proproin序列的第52个氨基酸。我们进行了实验，以确定宿主细胞因子在丙proproin成熟中的参与。在LepBts（先导肽酶B）宿主的非允许温度下，proprolin加工被抑制。此外，在这些条件下，只观察到全长前体，这表明LepB负责整个proproin先导肽的去除。使用proprolin加工作为proprolin插入质膜的测量，我们发现SecA和SecY的抑制或耗尽不影响proprolin成熟。一般的膜扰动如乙醇的加入也没有影响。然而，质子动力的耗散确实导致了proprolin加工的明显抑制，这表明膜插入需要这种能量源。我们认为proprolin在质膜中的插入过程独立于SecA-SecY分泌机制，但需要质子动力。这些结果提出了一个模型，其中proproin插入导致先导肽酶B加工生成7-kDa肽，然后在TraX存在下乙酰化。
F pilin is the subunit required for the assembly of conjugative pili on the cell surface of Escherichia coli carrying the F plasmid. Maturation of the F-pilin precursor, propilin, involves three F plasmid transfer products: TraA, the propilin precursor; TraQ, which promotes efficient propilin processing; and TraX, which is required for acetylation of the amino terminus of the 7-kDa pilin polypeptide. The mature pilin begins at amino acid 52 of the TraA propilin sequence. We performed experiments to determine the involvement of host cell factors in propilin maturation. At the nonpermissive temperature in a LepBts (leader peptidase B) host, propilin processing was inhibited. Furthermore, under these conditions, only full-length precursor was observed, suggesting that LepB is responsible for the removal of the entire propilin leader peptide. Using propilin processing as a measure of propilin insertion into the plasma membrane, we found that inhibition or depletion of SecA and SecY does not affect propilin maturation. Addition of a general membrane perturbant such as ethanol also had no effect. However, dissipation of the proton motive force did cause a marked inhibition of propilin processing, indicating that membrane insertion requires this energy source. We propose that propilin insertion in the plasma membrane proceeds independently of the SecA-SecY secretion machinery but requires the proton motive force. These results present a model whereby propilin insertion leads to processing by leader peptidase B to generate the 7-kDa peptide, which is then acetylated in the presence of TraX.