Guest lecture by Yoshinori Fujiyoshi

CMBN is happy to announce the following guest lecture:

Recent advancements in structural analysis of AQP4 water channels and Cx26 gap junction channels

Professor Yoshinori Fujiyoshi, Department of Biophysics, Graduate School of Science, Kyoto University, Oiwake, Kitashirakawa, Sakyo-ku, Kyoto 606-8502, Japan

Thursday 24 September 2009 at 1515
Auditorium 13, Domus Medica, University of Oslo

Water channels, aquaporin-1 and -4 (AQP1 and AQP4) can permeate about 300 million water molecules in a second without permeation of any ions and even proton. Structure analysis of AQP1 by electron crystallography revealed peculiar structural determinants as well as water selective mechanism [Nature 407 (2000) 599-605]. By analyzing structure of another water channel, AQP0 at a resolution of 1.9 Å, we discriminated water molecules in the channel [Nature 438 (2005) 633-638]. AQP4 is the predominant water channel in brain and we are particularly interested in this channel. Structure analyses showed weak but specific interactions suggesting a structural role for the water channel in adhesion of membrane layers. We named this type channel as “Adhennel” family [J. Mol. Biol. 355 (2006) 628-639]. We recently improved the resolution of a mutant AQP4S180D and discriminated water molecules as well as lipid molecules in 2D crystals [J. Mol. Biol. 389 (2009) 694-706]. The analysis at higher resolution by electron crystallography proved a model named as hydrogen bond isolation mechanism by which we explained the molecular mechanism of water channels with fast and high water selective function. Structure of an Adhennel, connexion-26 (Cx26) Gap Junction channel was also analyzed and we proposed a plug gating model [PNAS 104 10034-10039 (2007)]. We also analyzed structure of Cx26 at an open state by X-ray crystallography [Nature 458 (2009) 597-602] and are challenging to understand the complex gating mechanism of gap junction channels. By focusing on multifunctional channels, I would like to introduce recent results in structural physiology of membrane proteins by utilizing our cryo-electron microscope with helium cooled specimen stage.