Yoshinori Fujiyoshi
Cellular and Structural Physiology Institute (CeSPI), Nagoya University, Furo-cho, Chikusa, Nagoya 464-8601, Japan

I am personally interested in molecular mechanisms, how education and other experiences during human development influence cognitive ability and personality in the adult. For understanding brain and other biological functions from molecular level, structure analyses of membrane proteins are quite-efficacious. We therefore developed a cryo-EM with helium cooled specimen stage [1]. As an example showing usefulness of the cryo-EM, we could discriminate 8 water molecules in the water channel AQP4 [2], which is the predominant water channel in brain, while their densities were blurred in the higher resolution structure by X-ray crystallography [3]. The counterintuitive notion could be attributed to the difference of surround atmosphere for structure analyses of membrane proteins. The characteristic distribution of the dielectric constants in membrane produces large dipole moment of the two short helices of water channels, whereas the dipole moment without lipid bilayer is very small. In cooperation with the electrostatic field of the two short helices, the carbonyl groups in the channel act as binding sites in the narrow channel with highly hydrophobic surface and lower the energy barrier for water molecules entering the narrow water channel. These water stable positions guided by the polypeptide carbonyl and amide groups of highly conserved NPA motifs may make 3 billion water molecules pass through the channel in a second. These structural studies strongly suggested that electron crystallography, which was established in MRCLMB, is very powerful method for understanding physiological functions of membrane proteins. However, the necessity of crystallization makes this method less popular in the structural biology field. By single particle analysis, many structures have recently been analysed, and we also used this method and analysed structure of gap junction channel in very short period [4]. The dramatic change in this field enables us to challenge to develop a new strategy named as drug rescuing for drug development. Many lead compounds as well as target proteins have to be thrown into garbage box because of adverse effects. We will be able to rescue the target and compounds as a drug candidate by modifying the ligand chemical on the unrelated parts for pharmacologic action. Structural information of the ligand and membrane protein complex is important for the modification, and the higher resolution of structure analysis is achieved, the more useful for drug development the analysis is. Therefore, we started to develop a new cryo-EM with helium cooled specimen stage, 8th generation cryo-EM, which may make us possible to analyse high resolution structure. I would like to introduce possible design of the 8th generation together with our results in a field named as structural physiology.

References

[1] Y Fujiyoshi, Adv. Biophys., 35, 25-80 (1998). [2] K Tani et al., J. Mol. Biol., 389, 694-706 (2009). [3] JD Ho et al., Proc. Natl. Acad. Sci. USA, 106, 7437-7442 (2009). [4] A Oshima et al., Nature Comms, 7, 13681 (2016).

External speaker: Frank Uhimann, Francis Crick Institute, London