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Phospholipid-dependent regulation of the motor activity of myosin X
Umeki, Nobuhisa,Jung, Hyun Suk,Sakai, Tsuyoshi,Sato, Osamu,Ikebe, Reiko,Ikebe, Mitsuo Nature Publishing Group, a division of Macmillan P 2011 Nature structural & molecular biology Vol.18 No.7
Myosin X is involved in the reorganization of the actin cytoskeleton and protrusion of filopodia. Here we studied the molecular mechanism by which bovine myosin X is regulated. The globular tail domain inhibited the motor activity of myosin X in a Ca<SUP>2+</SUP>-independent manner. Structural analysis revealed that myosin X is monomeric and that the band 4.1-ezrin-radixin-moesin (FERM) and pleckstrin homology (PH) domains bind to the head intramolecularly, forming an inhibited conformation. Binding of phosphatidylinositol-3,4,5-triphosphate (PtdIns(3,4,5)P<SUB>3</SUB>) to the PH domain reversed the tail-induced inhibition and induced the formation of myosin X dimers. Consistently, disruption of the binding of PtdIns(3,4,5)P<SUB>3</SUB> attenuated the translocation of myosin X to filopodial tips in cells. We propose the following mechanism: first, the tail inhibits the motor activity of myosin X by intramolecular head-tail interactions to form the folded conformation; second, phospholipid binding reverses the inhibition and disrupts the folded conformation, which induces dimer formation, thereby activating the mechanical and cargo transporter activity of myosin X.
The tail binds to the head-neck domain, inhibiting ATPase activity of myosin VIIA.
Umeki, Nobuhisa,Jung, Hyun Suk,Watanabe, Shinya,Sakai, Tsuyoshi,Li, Xiang-dong,Ikebe, Reiko,Craig, Roger,Ikebe, Mitsuo National Academy of Sciences 2009 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.106 No.21
<P>Myosin VIIA is an unconventional myosin, responsible for human Usher syndrome type 1B, which causes hearing and visual loss. Here, we studied the molecular mechanism of regulation of myosin VIIA, which is currently unknown. Although it was originally thought that myosin VIIA is a dimeric myosin, our electron microscopic (EM) observations revealed that full-length Drosophila myosin VIIA (DM7A) is a monomer. Interestingly, the tail domain markedly inhibits the actin-activated ATPase activity of tailless DM7A at low Ca(2+) but not high Ca(2+). By examining various deletion constructs, we found that deletion of the distal IQ domain, the C-terminal region of the tail, and the N-terminal region of the tail abolishes the tail-induced inhibition of ATPase activity. Single-particle EM analysis of full-length DM7A at low Ca(2+) suggests that the tail folds back on to the head, where it contacts both the motor core domain and the neck domain, forming an inhibited conformation. We concluded that unconventional myosin that may be present a monomer in the cell can be regulated by intramolecular interaction of the tail with the head.</P>
Miyamoto, Yoichi,Umeki, Hiroyuki,Ohsawa, Hideaki,Naito, Morimasa,Nakano, Katsushi,Makino, Hitoshi,Shimizu, Kazuhiko,Seo, Toshihiro Korean Nuclear Society 2006 Nuclear Engineering and Technology Vol.38 No.6
Ensuring sufficient supplies of clean, economic and acceptable energy is a critical global challenge for the 21st century. There seems little alternative to a greatly expanded role for nuclear power, but implementation of this option will depend on ensuring that all resulting wastes can be disposed of safely. Although there is a consensus on the fundamental feasibility of such disposal by experts in the field, concepts have to be developed to make them more practical to implement and, in particular, more acceptable to key stakeholders. By considering global trends and using illustrative examples from Japan, key areas for future R&D are identified and potential areas where the synergies of international collaboration would be beneficial are highlighted.
A Behavior of the Diffuser Rotating Stall in a Low Specific Speed Mixed-Flow Pump
Miyabe, Masahiro,Furukawa, Akinori,Maeda, Hideaki,Umeki, Isamu,Jittani, Yoshinori Korean Society for Fluid machinery 2009 International journal of fluid machinery and syste Vol.2 No.1
The flow instability in a low specific speed mixed-flow pump, having a positive slope of head-flow characteristics was investigated. Based on the static pressure measurements, it was found that a rotating stall in the vaned diffuser occurs at about 65% flow rate of best efficiency point (BEP). A dynamic Particle Image Velocimetry (DPIV) measurement and the numerical simulations were conducted in order to investigate the flow fields. As a result, the diffuser rotating stall was simulated even by Computational Fluid Dynamics (CFD) and the calculated periodic flow patterns agree well with the measured ones by DPIV. It is clarified that a periodical large scaled backflow, generated at the leading edge of the suction surface of the diffuser vane, causes the instability. Furthermore, the growth of the strong vortex at the leading edge of the diffuser vane induces the strong backflow from the diffuser outlet to the inlet. The scale of one stall cell is covered over four-passages in total thirteen vane-passages.
TETSUO KUBO,TOMOFUMI YAMAMOTO,KUNIHIKO SATO,MASAKAZU JIMBO,TETSUO IMAOKA,YOSHITO UMEKI 한국원자력학회 2014 Nuclear Engineering and Technology Vol.46 No.5
A feasibility study on the seismic design of nuclear reactor buildings with application of a seismic isolation systemis introduced. After the Hyogo-ken Nanbu earthquake in Japan of 1995, seismic isolation technologies have been widelyemployed for commercial buildings. Having become a mature technology, seismic isolation systems can be applied toNPP facilities in areas of high seismicity. Two reactor buildings are discussed, representing the PWR and BWR buildingsin Japan, and the application of seismic isolation systems is discussed. The isolation system employing rubber bearingswith a lead plug positioned (LRB) is examined. Through a series of seismic response analyses using the so-named standarddesign earthquake motions covering the design basis earthquake motions obtained for NPP sites in Japan, the responsesof the seismic isolated reactor buildings are evaluated. It is revealed that for the building structures examined herein: (1)the responses of both isolated buildings and isolating LRBs fulfill the specified design criteria; (2) the responses obtainedfor the isolating LRBs first reach the ultimate condition when intensity of motion is 2.0 to 2.5 times as large as that of thedesign-basis; and (3) the responses of isolated reactor building fall below the range of the prescribed criteria.
Kubo, Tetsuo,Yamamoto, Tomofumi,Sato, Kunihiko,Jimbo, Masakazu,Imaoka, Tetsuo,Umeki, Yoshito Korean Nuclear Society 2014 Nuclear Engineering and Technology Vol.46 No.5
A feasibility study on the seismic design of nuclear reactor buildings with application of a seismic isolation system is introduced. After the Hyogo-ken Nanbu earthquake in Japan of 1995, seismic isolation technologies have been widely employed for commercial buildings. Having become a mature technology, seismic isolation systems can be applied to NPP facilities in areas of high seismicity. Two reactor buildings are discussed, representing the PWR and BWR buildings in Japan, and the application of seismic isolation systems is discussed. The isolation system employing rubber bearings with a lead plug positioned (LRB) is examined. Through a series of seismic response analyses using the so-named standard design earthquake motions covering the design basis earthquake motions obtained for NPP sites in Japan, the responses of the seismic isolated reactor buildings are evaluated. It is revealed that for the building structures examined herein: (1) the responses of both isolated buildings and isolating LRBs fulfill the specified design criteria; (2) the responses obtained for the isolating LRBs first reach the ultimate condition when intensity of motion is 2.0 to 2.5 times as large as that of the design-basis; and (3) the responses of isolated reactor building fall below the range of the prescribed criteria.