IV型菌毛回缩的波动
Fluctuations in type IV pilus retraction
摘要：
IV型菌毛回缩马达存在于许多重要的细菌病原体中。它是已知最强的直线电动机蛋白，是细菌感染性所必需的。我们的特点IV型菌毛退缩的随机化学反应模型的动力学。我们发现，两态模型可以描述实验力-速度关系和ATP浓度的定性依赖性。结果表明，动力学是有限的ATP依赖的步骤在低负荷和力依赖的步骤在高负荷，并且至少有一个步骤是有效的不可逆的力的测量范围内。子步骤的不可逆性质导致对未来实验的有趣预测：我们发现不同的参数化具有数学上相同的力-速度关系，但波动（扩散常数）不同。我们还发现了一个较长的基本步骤相比，早期的分析，这更好地同意与已知的事实的结构的菌毛丝和精力充沛的考虑。我们的结论是，需要更多的实验数据，进一步的回缩实验可能会解决有趣的细节，并提供有价值的见解PilT机械。根据我们的研究结果，收缩动力学的波动成为未来实验中要研究的关键属性。
英文摘要：
The type IV pilus retraction motor is found in many important bacterial pathogens. It is the strongest known linear motor protein and is required for bacterial infectivity. We characterize the dynamics of type IV pilus retraction in terms of a stochastic chemical reaction model. We find that a two state model can describe the experimental force velocity relation and qualitative dependence of ATP concentration. The results indicate that the dynamics is limited by an ATP-dependent step at low load and a force-dependent step at high load, and that at least one step is effectively irreversible in the measured range of forces. The irreversible nature of the sub-step(s) lead to interesting predictions for future experiments: We find different parameterizations with mathematically identical force velocity relations but different fluctuations (diffusion constant). We also find a longer elementary step compared to an earlier analysis, which agrees better with known facts about the structure of the pilus filament and energetic considerations. We conclude that more experimental data is needed, and that further retraction experiments are likely to resolve interesting details and give valuable insights into the PilT machinery. In light of our findings, the fluctuations of the retraction dynamics emerge as a key property to be studied in future experiments.
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