The flagellar motor of Bacillus subtilis possesses two distinct H+-type MotAB and Na+-type MotPS stators. In contrast to the MotAB motor, the MotPS motor functions efficiently at elevated viscosity in the presence of 200 mM NaCl. Here, we analyzed the torque-speed relationship of the Bacillus MotAB and MotPS motors over a wide range of external loads. The stall torque of the MotAB and MotPS motors at high load was about 2,200 pN nm and 220 pN nm, respectively. The number of active stators in the MotAB and MotPS motors was estimated to be about ten and one, respectively. However, the number of functional stators in the MotPS motor was increased up to ten with an increase in the concentration of a polysaccharide, Ficoll 400, as well as in the load. The maximum speeds of the MotAB and MotPS motors at low load were about 200 Hz and 50 Hz, respectively, indicating that the rate of the torque-generation cycle of the MotPS motor is 4-fold slower than that of the MotAB motor. Domain exchange experiments showed that the C-terminal periplasmic domain of MotS directly controls the assembly and disassembly dynamics of the MotPS stator in a load- and polysaccharide-dependent manner.

homologs of MotA arid MotB in the H'-driven flagellar motor of Escherichia coli, form a stator complex in the Na'-driven flagellar motor of M'brio aiginolyticus. The motor torque is generated by the interaction between the cytoplasmic domain of PomA and the C-terminal domain of FliG, a cornponent of the rotor, ]t was shown that a tandem fused PomA is functiona] as a torque generator in Z aiginolyti{'us (Sato and Homma, JBC 2000). Furthermore, a ehimeric stator (which consists of PornA and the chimeric fugion protein PotB} works as a Na'-driven flage]laT rnotor in E, coli (Asai et al,, JMB 2003}. In the last annual meeting, we demonstrated that tandem PomA dimer was expressed as a single polypeptide in E. eoii and swjmming speed ofE.coti cells with tandem PomA was about haJfofthat with the monomeric PemA, suggesting that tandem Po]nA functions as a torque

ILuh,(GraduateSchooioj'Scienee,Nago),aLinivei"'ity)

No abstract

Biological system is unique in that component biomolecules are selforganized and emerge adaptable, stable and energy-saving functions. To understand the essential condition for reproducing the properties and constructing stable system from unstable flexible components, we are designing artificial muscle using myosin and DNA nanostructure. System size, spatial positioning, degree of intrinsic noise and the mechanical communication in the synthesized muscle can be modulated and we'll observe the internal dynamics and the system behavior at the single molecule resolution. We have developed several novel tools to modulate the system and monitor the internal dynamics with high precision. 3P141 ナノスリット基板を用いたアクチンの重合の観察Observation of actin polymerization in linear zero-mode Alkaliphilic Bacillus pseudofirmus OF4 has a MotPS complex as a stator and the flagellum is driven by a Na + -motive force. Previous studies showed that strain OF4 swimming is dependent on Na + at pH 8-10, but exhibited poor motility at neutral pH even in the presence of Na + . It was hypothesized there could be competitive inhibition by H + of the Na + translocation by the stator-force generator MotPS. In contrast, B. subtilis has a MotPS complex similar to strain OF4, but it was reported that B. subtilis can swim dependent on Na + concentrations at neutral pH. We investigated important amino acid residues for the motility decrease at neutral pH of the alkaliphilic Bacillus. Critical amino acid residues for reduced motility at neutral pH were identified in the MotP subunit. 3P143アクトミオシン複合体におけるミオシン・サブフラグメント １の首振り運動の分子動力学シミュレーション Molecular dynamics simulation for the swinging lever-arm motion of a myosin subfragmnet-1 in an actomyosin complexTadashi Masuda (Fukushima Univ.)Molecular dynamics simulation was conducted for an actomyosin complex consisting of a myosin subfragment-1 and seven actin monomers solved in water. External force was applied to the end of the neck domain in the direction opposite to the power stroke by using the "pull code" in the GROMACS software. The myosin neck domain showed a swinging lever-arm motion from the post-power stroke position to the pre-power stroke position, while the myosin head did not detach from the actin filament. This motion was in accordance with the myosin power stroke mechanism named "Driven by Detachment (DbD)" theory, which assumes that the power stroke is caused by the elasticity at the joint between the head and the neck domains and is not directly related to ATP hydrolysis. Recent experiments on F1-ATPase have clarified that the dissipative heat inside the motor is very small, irrespective of the velocity of rotation and energy transport. In this presentation, we focus on the problem that the amount of internal dissipation is not simply determined by the sequence of equilibrium pictures, but also relies on the truely nonequilibrium aspect. We show that the totally asymmetric affinity model, where ATP binding to F1 is assumed to have low dependence on the angle of the rotating shaft, produces results th...