Intra-molecule Motion of Functional Proteins at Single Molecule Level Using Diffracted X-ray Tracking

Most soluble proteins are composed of several subunits and the protein’s function could be expressed by changing its intra-structure or its relative position in the multimeric protein. Moreover, 80 % of the drug targets are membrane proteins that are also composed of several subunits. Therefore, it would be important to obtain such cooperative motion of each subunit to understand the mechanism of functional proteins. This motion is thought be small as atomic scale, and fast at the microsecond level. Therefore, a technique to get such dynamic information is desired in both academic and industrial research.

We have proposed a single molecule technique that utilizes short wavelength probes of X-rays to monitor the internal motions of a single protein. We call it diffracted X-ray tracking (DXT) [1,2] and it would be a powerful technique in biological science for detecting atomic-scale dynamic motion of the protein at the single molecular level with several tens of microseconds time resolution. In DXT, a target protein is labeled with a nanocrystal with a size of several tens of nanometers and the motions of the nanocrystal coupled with the protein’s motions are recorded as the trajectories of the Laue spots from the nanocrystal.

In this seminar, we will present recent DXT results for dynamic motion of multimeric proteins [3-6] and discuss the future direction of this method.

References

1. Y. C. Sasaki et al., Phys. Rev. E 62:3843 (2000) DOI: 10.1103/PhysRevE.62.3843
2. H. Shimizu et al., Cell 132:67 (2008) DOI: 10.1016/j.cell.2007.11.040
3. H. Sekiguchi et al., PLoS ONE 8:e64176 (2013) DOI: 10.1371/journal.pone.0064176
4. K. Ichiyanagi et al., Rev. Sci. Instrum.84:103701 (2013) DOI: 10.1063/1.4819305
5. H. Sekiguchi et al., Scientific Reports 4:6384 (2014) DOI: 10.1038/srep06384
6. H. Kozono et al., Biophys. J. 108:350 (2015) DOI: 10.1016/j.bpj.2014.12.004