3P138 The structural role of the Pro-Ala-rich extension of the troponin-I of bumblebee flight muscle(10. Muscle,Poster)
We observed the adsorption process of myosin to the gold surface by QCM (quartz crystal microbalance). Viscoelastic property of the myosin adsorbed to the surface of the gold electrode and its surrounding solution as a whole was studied using the AFFINIXQN Pro (Initium, Tokyo), When myosin adsorbed more sparsely than 0.2 ug/cm 2 , viscoelastic change accompanied with myosin adsorption was almost the same as to a solid globular protein. On the other hand, when myosin adsorbed at higher density,
... at higher density, large viscoelastic change has been obserbed. Viscoelastic analysis indicates that myosin plays as a protein having viscoelasticity, and that binding ATP or ADP to myosin head changes the viscoelasticity of the protein. 3P135 ホッキ貝柱筋と牽引筋の天然アクトミオシン (NAM=M+A+TM1 or TM2)の「Mg-ATPase 活性の Ca 依存 性」と「TM アイソフォーム TM1 と TM2 の組成比」 Hokki clam retractor muscle NAM Mg-ATPase activities and seasonal changes of TM1 and TM2 isoform contents Yoichi Yazawa (Univ. Hokkaido Education) We have studied about protein components actomyosin(NAM)of retractor and adductor muscles of Hokki clam,Spisula sacchalinensis. In autumn (September~November), Ca sensitivities of NAM were (15~50%). M.W. of TM2 was 43.000. Them of NAM prepared in other three seasons were higher (88~97%). M.W. of TM1 was 32,000. TM2 were found in this report for the first time. Characterization of the structural and dynamic properties of hydration water around F-actin detected by neutron and X-ray scattering The structural and dynamic properties of hydration water around F-actin and myosin S1 were investigated using small-angle neutron/X-ray scattering and quasi-elastic neutron scattering. S1 was shown to have typical hydration water, which has 10-15% higher average density with lower mobility than bulk water. On the other hand, F-actin was shown to have hydration water with unusual properties: the average density of the hydration water is at least 19% higher than that of bulk water and mobility is close to that of bulk water. These results indicate the diversity of hydration shell around proteins in terms of both structural and dynamic properties. The unusual hydration water around F-actin may be related to the suggested existence of "hyper-mobile water" around F-actin. 3P137 ワタリガニ骨格筋における細いフィラメントの精製および低 温電子顕微鏡法による構造解析 Isolation of native thin filament from skeletal muscle for structural analysis by cryoEM Muscle contraction is caused by sliding between the thick and thin filaments by repeated association and dissociation of myosin head and actin and is regulated by intracellular Ca2+ concentration. The thin filament is composed of actin filament, tropomyosin (Tm), and troponin (Tn) complex (TnC, TnI, TnT). Ca2+ released from sarcoplasmic reticulum binds to TnC, leading to a conformational change of Tm on the actin filament. To understand the regulatory mechanism of muscle contraction by electron cryomicroscopy, we developed a method to isolate skeletal muscle thin filament from a crab, Portunus trituberculatus. The result of image analysis showed that only 25% of the isolated thin filaments were fully decorated with Tm and Tn. 3P138 マルハナバチ飛翔筋トロポニン I の長い延長部の構造的役割 The structural role of the Pro-Ala-rich extension of the troponin-I of bumblebee flight muscle Hiroyuki Iwamoto, Naoto Yagi (SPring-8, JASRI) The structural role of the unusually long extension of insect flight muscle (IFM)-specific isoform of troponin-I was examined by X-ray diffraction and electron microscopy. Electron microscopy revealed that, after enzymatic removal of the extension from bumblebee IFM, a substantial fraction of the thin filaments were at the trigonal position between three thick filaments, like in vertebrate skeletal muscle, while the rest of the thin filaments remained in their original position (midway between two neighboring thick filaments). This result explains the dramatic change in X-ray diffraction patterns after removal of the extension (from insect-type to vertebrate-type), and suggests that its role is to keep the filament lattice in the correct configuration for IFM. Actin is one of the most important proteins in eukaryotic cells. Actin has two states, G-actin and F-actin. We are interested in the transformation of G-to F-actin. We recorded the time-resolved small angle scattering intensities during actin polymerization at SPring-8 BL45XU. The actin polymerization was initiated by mixing of salt to G-actin prepared in the low salt solution. The time courses of SAXS intensity profiles were analyzed by using the sequential polymerization model. We concluded that actin formed dimer immediately after mixing of salt, and growth of filament was initiated when pentamer was formed by chance.