要 旨 |
Motor proteins are molecular machines
that convert the chemical energy derived from the hydrolysis
of ATP into mechanical work used to power cellular motility.
In addition to driving movement in specialized motile cells
like muscle fibers, motor proteins are found in all eukaryotic
cells where they transport organelles such as vesicles, mitochondria
and chromosomes from one part of the cell to another. The
focus of this seminar is on how motor proteins work. How
do they move? How much fuel do they consume, and with what
efficiency? How do chemical reactions generate force? What
is the role of thermal fluctuations? These questions are
especially fascinating because motor proteins are unusual
machines that do what no manmade machines do: they convert
chemical energy to mechanical energy directly, rather than
via an intermediate such as heat or electrical energy. Tremendous
insight into this chemomechanical energy transduction process
has come from technical developments over the last ten years
that allow single protein molecules to be detected and manipulated.
The goal of this review is to provide a framework within
which to understand these new observations: how do mechanical,
thermal, and chemical forces converge as a molecular motor
moves along its filamentous track. For background, the reader
is directed to Molecular Biology of the Cell (Alberts et
al., 2002) for an introduction to the biology of cells and
molecules, to Cell Movements (Bray, 2000) for a broad review
of cell motility, and to Mechanics of Motor Proteins and
the Cytoplasm (Howard, 2001) for more detailed discussion
of the mechanics of molecular motors and the cytoskeleton. |