Biology Reference
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(
O
/
C
/
C'
)
(
C'
/
O
/
C
)
(
C
/
C'
/
O
)
C
(
D
)
O
(
E
)
C'
(
T
)
1
2
-1
-2
C'
(
T
)
O
(
E
)
C
(
D
)
C'
(
T)
C
(
D
)
O
(
E
)
-3
3
Fig. 7.3 The pre-fit mechanism of the rotary catalysis of F
1
-ATPase based on the generalized
Franck-Condon principle (GFCP) or the Principle of Slow and Fast Processes (PSFP).
O
¼
open
conformation;
C
¼
closed conformation whose shape is complementary to that of ADP;
C'
¼
closed conformation whose shape is complementary to that of ATP;
E
¼
no ligand, that is, empty;
T
3
stator ring (also called the F
1
-ATPase
stator ring) that catalyzes the hydrolysis of ATP to ADP and inorganic phosphate, P
i
. Although
experimentally only the O conformation could be detected by the high-speed AFM (Uchihashi
et al. 2011), it is predicted here that there will be found two other conformations, designated as C
and C' in this figure that circulate counter clockwise around the F
1
-ATPase stator ring in phase
with the O conformation. The
solid arrows
(see Steps 1, 2 and 3) indicate the direction of
conformational transitions occurring in the presence of excess ATP relative to ADP in the medium,
while the
dotted arrows
(see Steps -1, -2 and -3) indicate the direction of motions in the presence of
excess ADP and Pi relative to ATP
¼
ATP;
D
¼
ADP. The
filled triangle
stands for the
a
b
3
associated ligand-binding events, because the former is a slower process than the
latter. For example, when that F
1
stator undergoes the transition from State
1
to
State
3
in Fig.
7.4
, the conformations of the
subunits change from (O/C/C') to
(C'/O/C) and the ligand system changes from (E/D/T) to (T/E/D). But, because
the conformation changes are slower than the ligand-binding events, the transi-
tion from State
1
to State
3
cannot occur unless and until State
1
undergoes a
transition to an intermediate state, State
2
, by first changing the conformational
state from (O/C/C') to (OC'/CO/C'C), which is a high-energy state as indicated
by the superscript double dagger and leads to the transition of the ligand-binding
state from (E/D/T) to (E,T/D,E/T,D). As one can see, State
2
is intermediate
between states
1
and
3
in both the
conformational states
of the proteins and the
associated
ligand systems
, thus satisfying the
Principle of Microscopic Revers-
to State
3
, in which case the ligand-binding state spontaneously changes from
(E,T/D,E/T,D) to (T/E/D). The mechanisms of the state transitions from
3
to
5
and from
5
to
1
as shown in Fig.
7.4
are all similar to the state transitions from
b
