Electron crystallography is especially useful for studying the structure and function of membrane proteins — key molecules with important functions in neural and other cells. Electron crystallography is now an established technique for analyzing the structures of membrane proteins in lipid bilayers that closely simulate their natural biological environment. Utilizing cryo-electron microscopes with helium-cooled specimen stages that were developed through a personal motivation to understand the functions of neural systems from a structural point of view, the structures of membrane proteins can be analyzed at a higher than 3 Å resolution. This review covers four objectives. First, I introduce the new research field of structural physiology. Second, I recount some of the struggles involved in developing cryo-electron microscopes. Third, I review the structural and functional analyses of membrane proteins mainly by electron crystallography using cryo-electron microscopes. Finally, I discuss multifunctional channels named “adhennels” based on structures analyzed using electron and X-ray crystallography.
Originating from cancer research in mammalian cultured cells, the entirely new field of the unfolded protein response (UPR) was born in 1988. The UPR is a transcriptional induction program coupled with intracellular signaling from the endoplasmic reticulum (ER) to the nucleus to maintain the homeostasis of the ER, an organelle which controls the quality of proteins destined for the secretory pathway. Extremely competitive analyses using the budding yeast Saccharomyces cerevisiae revealed that although signaling from both the ER and cell surface is initiated by activation of a transmembrane protein kinase, the mechanism downstream of ER-resident Ire1p, a sensor molecule of the UPR, is unique. Thus, unconventional spliceosome-independent mRNA splicing is utilized to produce the highly active transcription factor Hac1p. This is the autobiographical story of how a young and not yet independent scientist competed with a very famous full professor in the early days of UPR research, which ultimately lead to their sharing Lasker Basic Medical Research Award in 2014.
Substantial progress in research on the recession of coastal cliffs composed of soft materials has been made in recent years and data with higher accuracy have been accumulated. This paper provides the state of the art review in the recession studies and highlights two new findings obtained from the reanalysis of existing data. The review topics are: episodic and localized nature of cliff recession; the development of cliffline; the relationship between cliff height and recession rate; mechanisms of cliff toe erosion by waves; a fundamental equation for wave-induced toe erosion; factors controlling toe erosion; and slope instabilities and mass movements. The findings are presented on (1) the temporal change in cliffline recession mode and (2) the effect of beach sediment at the cliff base on the cliff erosion.
In conventional muography observations using two detectors for muon tracking, the accidental coincidence of vertical electromagnetic showers generates identical trajectories to the muon tracks. Although muography has favorable properties, which allow direct density measurements inside a volcano, the measured density is lower than the actual value due to these fortuitous trajectories. We performed muography of Usu volcano, and confirmed that, in comparison with a use of two detectors, background noise levels were reduced by more than one order of magnitude using seven detectors for selecting linear trajectories. The resultant muographic image showed a high-density region underneath the central region of Usu volcano. This picture is consistent with the magma intrusion model proposed in previous studies. To clarify the three-dimensional location and actual size of the detected high-density body, multidirectional muographic measurements are necessary.