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首页> 外文期刊>Journal of Molecular Biology >Kinetic basis for the competitive recruitment of TolB by the intrinsically disordered translocation domain of colicin E9
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Kinetic basis for the competitive recruitment of TolB by the intrinsically disordered translocation domain of colicin E9

机译：耐凝固素易位域竞争招募的动力学依据

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摘要

TolB and Pal are members of the Tol-Pal system that spans the cell envelope of Gram-negative bacteria and contributes to the stability and integrity of the bacterial outer membrane (OM). Lipoylated Pal is tethered to the OM and binds the β-propeller domain of periplasmic TolB, which, as recent evidence suggests, disengages TolB from its interaction with other components of the Tol system in the inner membrane. Antibacterial nuclease colicins such as colicin E9 (ColE9) also bind the β-propeller domain of TolB in order to catalyze their translocation across the bacterial OM. In contrast to Pal, however, colicin binding to TolB promotes its interaction with other components of the Tol system. Here, through a series of pre-steady-state kinetic experiments utilizing fluorescence resonance energy transfer pairs within the individual protein-protein complexes, we establish the kinetic basis for such 'competitive recruitment' by the TolB-binding epitope (TBE) of ColE9. Surprisingly, the 16-residue disordered ColE9 TBE associates more rapidly with TolB than Pal, a folded 13-kDa protein. Moreover, we demonstrate that calcium ions, which bind within the confines of the TolB β-propeller domain tunnel and are known to increase the affinity of the TolB-ColE9 complex, do not exert their influence through long-range electrostatic effects, as had been predicted, but through short-range effects that slow the dissociation rate of ColE9 TBE from its complex with TolB. Our study demonstrates that an intrinsically disordered protein undergoing binding-induced folding can compete effectively with a globular protein for a common target by associating more rapidly than the globular protein.
机译：TOLB和PAL是托巴尔PAL系统的成员，跨越革兰氏阴性细菌的细胞包络，有助于细菌外膜的稳定性和完整性。脂肪化的PAL将其束缚至OM并结合周质TOLB的β-螺旋桨结构域，随着最近的证据表明，这种β-螺旋桨结构域在其与内膜中的托系统的其他组分的相互作用中脱离TOLB。诸如肠道E9（COLE9）的抗菌病症含有菌株，也结合TOLB的β-螺旋桨结构域，以催化它们穿过细菌OM的易位。然而，与PAL相比，与TOLB的耐凝聚蛋白结合促进其与TOL系统的其他组分的相互作用。这里，通过在单个蛋白质 - 蛋白复合物内使用荧光共振能量转移对的一系列预稳态动力学实验，我们通过COLE9的TOLB结合表位（TBE）来建立这种“竞争招募”的动力学依据。令人惊讶的是，16-残基紊乱的COLE9 TBE与TOLB比PAL更快速地联系，折叠的13kDa蛋白。此外，我们证明钙离子在β-螺旋桨结构域隧道的范围内结合，并且已知提高TOLB-COLE9复合物的亲和力，请不要通过远程静态效应来施加它们的影响预测，但通过短距离效应，使COLE9 TBE与TOLB复合物的解离率慢。我们的研究表明，经历结合诱导的折叠的本质无序蛋白质可以通过比球状蛋白更快地与球状靶向与常见目标有效竞争。

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