Preface
In this book, we present a view on the mechanism of functional expression of an
ATP-driven molecular motor (a protein or protein complex). It is substantially
different from the prevailing view that the molecular motor converts the chemical
energy stored in an ATP molecule or the free energy of ATP hydrolysis reaction to
mechanical work. We point out that this concept of chemo-mechanical coupling is
problematic and inconsistent with some of the recent experimental observations.
The molecular motor acts as a catalyst for the ATP hydrolysis reaction, an irreversible process, with the result that it is involved in the ATP hydrolysis cycle
comprising the ATP binding to the molecular motor, ATP hydrolysis, and dissociation of ADP and Pi from the molecular motor. During this cycle, the molecular
motor exhibits sequential changes in its configuration for minimizing the system
free energy. Here, the system comprises not only the molecular motor but also
water in which ATP, ADP, and Pi are dissolved. The system performs essentially
no mechanical work. The force which moves the protein or rotates a protein in the
complex is generated by not ATP but water. The effect of translational displacement
of water molecules in the entire system makes a dominant contribution to the force
generation. On the basis of the new view in which this entropic force by water plays
a pivotal role, we unveil the mechanism of unidirectional rotation of the central
shaft in F 1 -ATPase. This book describes the latest ideas of the author which have
not been published yet.
Uji/Chiba, Japan
Masahiro Kinoshita
v
In this book, we present a view on the mechanism of functional expression of an
ATP-driven molecular motor (a protein or protein complex). It is substantially
different from the prevailing view that the molecular motor converts the chemical
energy stored in an ATP molecule or the free energy of ATP hydrolysis reaction to
mechanical work. We point out that this concept of chemo-mechanical coupling is
problematic and inconsistent with some of the recent experimental observations.
The molecular motor acts as a catalyst for the ATP hydrolysis reaction, an irreversible process, with the result that it is involved in the ATP hydrolysis cycle
comprising the ATP binding to the molecular motor, ATP hydrolysis, and dissociation of ADP and Pi from the molecular motor. During this cycle, the molecular
motor exhibits sequential changes in its configuration for minimizing the system
free energy. Here, the system comprises not only the molecular motor but also
water in which ATP, ADP, and Pi are dissolved. The system performs essentially
no mechanical work. The force which moves the protein or rotates a protein in the
complex is generated by not ATP but water. The effect of translational displacement
of water molecules in the entire system makes a dominant contribution to the force
generation. On the basis of the new view in which this entropic force by water plays
a pivotal role, we unveil the mechanism of unidirectional rotation of the central
shaft in F 1 -ATPase. This book describes the latest ideas of the author which have
not been published yet.
Uji/Chiba, Japan
Masahiro Kinoshita
v