When T cells recognize their cognate antigens with MHCs on antigen-presenting cells, TCRs are gathering to form a signalosome, so-called a TCR microcluster, which is constructed by kinases and adaptors in their downstream. The other receptors expressing on T cells, such as a set of costimulatory receptors, also form microclusters and possess their own characteristic signals. Various signalosomes on a plasma membrane all together regulate T cell activation in a spatiotemporal fashion.
Ion permeation through ion channels is essential for life. Since the determination of the x-ray crystal structure of the K+ channel, extensive molecular dynamics (MD) studies have been performed to visualize ion permeation through the channel. However, the mechanism underlying how the experimentally measured current amplitudes are determined still remains elusive. Here, we examined the MD-simulated trajectories of ion permeation through the Kv1.2 channel by developing a method analyzing the dynamics of ions. The analysis clarified that the entrance of ions into the channel determines the permeation rate.
At SACLA, we are developing a data collection system focusing on dynamic crystallography putting a particular effort on membrane proteins. An experimental system for pump-probe experiments based on serial femtosecond crystallography using a viscous material injector has been developed. We used time-resolved serial femtosecond crystallography to visualize conformational changes in bR from nanoseconds to milliseconds following photoactivation. The cascade of structural changes throughout the protein shows how motions are choreographed as bR transports protons. We have also applied this system to study the light-induced structural changes and the site of O=O bond formation in photosystem II.