Holdbrook Daniel A, Burmann Björn M, Huber Roland G, Petoukhov Maxim V, Svergun Dmitri I, Hiller Sebastian, Bond Peter J
Bioinformatics Institute (A∗STAR), 30 Biopolis Street, #07-01 Matrix, 138671 Singapore, Singapore.
Biozentrum, University of Basel, Klingelbergstrasse 70, 4056 Basel, Switzerland.
Structure. 2017 Jul 5;25(7):1079-1088.e3. doi: 10.1016/j.str.2017.05.018. Epub 2017 Jun 22.
The trimeric periplasmic holdase chaperone Skp binds and stabilizes unfolded outer membrane proteins (OMPs) as part of bacterial OMP biogenesis. Skp binds client proteins in its central cavity, thereby reducing its backbone dynamics, but the molecular mechanisms that govern Skp dynamics and adaptation to differently sized clients remains unknown. Here, we employ a combination of microsecond timescale molecular dynamics simulation, small-angle X-ray scattering, and nuclear magnetic resonance spectroscopy to reveal that Skp is remarkably flexible, and features a molecular spring-loaded mechanism in its "tentacle" arms that enables switching between two distinct conformations on sub-millisecond timescales. The conformational switch is executed around a conserved pivot element within the coiled-coil structures of the tentacles, allowing expansion of the cavity and thus accommodation of differently sized clients. The spring-loaded mechanism shows how a chaperone can efficiently modulate its structure and function in an ATP-independent manner.
三聚体周质分子伴侣Skp作为细菌外膜蛋白（OMP）生物合成的一部分，结合并稳定未折叠的外膜蛋白。Skp在其中心腔中结合客户蛋白，从而降低其主链动力学，但控制Skp动力学以及适应不同大小客户蛋白的分子机制仍不清楚。在这里，我们结合使用微秒级分子动力学模拟、小角X射线散射和核磁共振光谱，揭示Skp具有显著的灵活性，并且在其“触手”臂中具有分子弹簧加载机制，能够在亚毫秒时间尺度上在两种不同构象之间切换。构象转换围绕触手卷曲螺旋结构内的保守枢轴元件进行，从而使腔扩张，进而容纳不同大小的客户蛋白。这种弹簧加载机制展示了一种分子伴侣如何以不依赖ATP的方式有效调节其结构和功能。
