2002 Fiscal Year Final Research Report Summary
Effective temperature of proteins in the active states
| Project/Area Number |
12304022
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
物理学一般
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| Research Institution | Osaka University |
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Principal Investigator |
YANAGIDA Toshio Graduate School of Frontier Biosciences, Professor, 生命機能研究科, 教授 (30089883)
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| Co-Investigator(Kenkyū-buntansha) |
IWANE Atsuko Graduate School of Frontier Biosciences, Assistant Professor, 生命機能研究科, 助手 (30252638)
SEKIMOTO Ken Institute of Basic Physics, Kyoto University, Professor, 基礎物理学研究所, 教授 (00179342)
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| Project Period (FY) |
2000 – 2002
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| Keywords | chemi-mechano coupling / thermal ratchet / Browninan movement / effective temperature / rotational elasticity / molecular motors / actomyosin |
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| Research Abstract |
Many proteins work using chemical energy that generates during hydrolysis of ATP into ADP and P1. A basic question, how proteins converts this chemical energy to mechanical works remains unsolved. The aims of this study were to examine if the effective temperature of a protein molecule excited by chemical energy of ATP is really increased and. If so, to construct a model to explain how chemical and mechanical energies are converted by a protein molecule. We chose actomyosin as the experimental system, and during the period of this grant, we obtained the following achievements.
(1) We have developed an experimental system to measure the effective temperature of an actin filament interacting with myosin molecules: an actin filament was horizontally held in solution being caught two microbeads attached to the both ends using double beam optical tweezers. Relative rotational Brownian movement of the two beads was measured and the effective temperature was calculated from the mean square of the angle between the two beads and the relaxation tirne.
(2) We have measured the rotational fluctuation of an actin filament interacting with myosin in the presence of ATP: Myosin VI, which has a 36nm step length per one ATP hydrolysis, rotated 45 degree during five 36nm steps. This movement cannot be explained according to simple walking model along the coiled actin filament.
(3) Myosin molecules are diffusing along the thermal ratchet of an actin filament. The ratio of forward and backward steps was measured using singlemolecule technique. The result indicates that difference of the energy barrier for forward and backward direction is 3kBT. This value is almost same for another protein motor kinesin.
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[Publications] Y, Inoue, A, H, Iwane, T, Miyai, E, Muto, T, Yanagida: "Motility of single one-headed kinesin molecules along microtubles"Biophys. J. 81. 2838-2850 (2001)
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