Peptide Probes Reveal a Hydrophobic Steric Ratchet in the Anthrax Toxin Protective Antigen Translocase.
Peptide Probes Reveal a Hydrophobic Steric Ratchet in the Anthrax Toxin Protective Antigen Translocase.
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肽探针揭示了炭疽毒素保护性抗原转位酶中的疏水性立体棘轮。
DOI：
10.1016/j.jmb.2015.09.007
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发表时间：
2015
影响因子：
5.6
通讯作者：
Krantz,BryanA
中科院分区：
文献类型：
--
作者：
Colby,JenniferM;Krantz,BryanA
炭疽毒素是炭疽杆菌在感染过程中产生的三方毒力因子。在酸性内体pH条件下，毒素的保护性抗原（PA）组分在宿主细胞中形成跨膜通道。PA通道然后在质子动力下将其两种酶组分（致死因子和水肿因子）易位到宿主细胞质中。蛋白质在质子动力作用下的转位是由一系列非特异性多肽结合位点催化的，称为钳位。一个10个残基的客体/宿主肽模型系统，KKKKKXXSXX，用于功能性探测野生型PA通道内的多肽钳相互作用。客体残基是Thr、Ala、Leu、Phe、Tyr和Trp。在稳态易位实验中，通道被具有增加的非极性表面积的肽阻断得最紧密。在含Trp的肽序列中观察到了协同肽结合，但在其他测试序列中没有观察到。色氨酸取代成一个灵活的，不带电荷的连接器之间的致死因子氨基末端结构域和白喉毒素A链加速易位。因此，移位酶通道中的肽钳位点可以感知肽中的大空间特征（如色氨酸），虽然这些空间相互作用可能使肽移位不良，但在折叠结构域的背景下，它们可以使蛋白质移位更快，推测是通过疏水空间棘轮机制。
Anthrax toxin is a tripartite virulence factor produced byBacillus anthracisduring infection. Under acidic endosomal pH conditions, the toxin's protective antigen (PA) component forms a transmembrane channel in host cells. The PA channel then translocates its two enzyme components, lethal factor and edema factor, into the host cytosol under the proton motive force. Protein translocation under a proton motive force is catalyzed by a series of nonspecific polypeptide binding sites, called clamps. A 10-residue guest/host peptide model system, KKKKKXXSXX, was used to functionally probe polypeptide-clamp interactions within wild-type PA channels. The guest residues were Thr, Ala, Leu, Phe, Tyr, and Trp. In steady-state translocation experiments, the channel blocked most tightly with peptides that had increasing amounts of nonpolar surface area. Cooperative peptide binding was observed in the Trp-containing peptide sequence but not the other tested sequences. Trp substitutions into a flexible, uncharged linker between the lethal factor amino-terminal domain and diphtheria toxin A chain expedited translocation. Therefore, peptide-clamp sites in translocase channels can sense large steric features (like tryptophan) in peptides, and while these steric interactions may make a peptide translocate poorly, in the context of folded domains, they can make the protein translocate more rapidly presumably via a hydrophobic steric ratchet mechanism.