3.4 Normal Rotation Under Solution Condition …
43
ATP
>
>
ATP H 2 O
ADP, Pi
>
>
: β-subunit
Pi
Category (1)
Category (2)
Fig. 3.14 Order of packing efficiency for β subunit to which ATP• • •H 2 O (see the caption for
Fig. 3.6), ATP, ADP + Pi, nothing, or Pi is bound. For example, the packing efficiency (PE) of a
β subunit to which ATP• • •H 2 O is bound is higher than the PE to which ATP is bound and much
higher than the PE to which Pi is bound. We also define ATP(ATP• • •H 2 O) (not shown here) as
an intermediate between ATP and ATP• • •H 2 O. The PE of the β subunit with ATP(ATP• • •H 2 O)
bound is lower than that with ATP• • •H 2 O bound but higher than that with ATP bound. Categories
(1) and (2) are defined as follows: A β subunit to which ATP• • •H 2 O, ATP, or ADP + Pi is bound
falls into category (1) whereas a β subunit to which nothing or Pi is bound falls into category (2)
(2) The packing efficiency of subcomplex I−γ, II−γ, or III−γ (i.e., the packing
structure of the α 3 β 3 complex) is determined in accordance with that of the β
subunit included in it. That is, as corroborated by our theoretical analyses, when
the packing efficiency for a β subunit follows the order, “β subunit in subcomplex
I−γ” < “β subunit in subcomplex II−γ” < “β subunit in subcomplex III−γ”,
the packing efficiency for a subcomplex follows the order, “subcomplex I−γ”
< “subcomplex II−γ” < “subcomplex III−γ”.
(3) The orientation of the γ subunit is optimized in response to the packing structure
of the α 3 β 3 complex. The retainment of the highly stabilized β DP −γ and α E −γ
contacts is especially important.
The packing structure of the α 3 β 3 γ complex possessing the specific nonuniformity
shown in Fig. 3.11 is highly stable in terms of the water entropy. Here, we define
categories (1) and (2) as indicated in Fig. 3.14. A β subunit to which ATP• • •H 2 O,
ATP, or ADP + Pi is bound falls into category (1) whereas a β subunit to which
nothing or Pi is bound falls into category (2). For the retainment of the high stability,
at least it is required that two of the three β subunits be in category (1) and the other β
subunit be in category (2). The α 3 β 3 γ complex is involved in the ATP hydrolysis cycle
during which the chemical compound bound to each β subunit (i.e., ATP• • •H 2 O,
ATP, ADP + Pi, nothing, or Pi) successively changes. Since the packing efficiency of
a β subunit is strongly dependent on the chemical compound bound to it as depicted
in Fig. 3.14, the packing efficiency of each β subunit successively changes during
the ATP hydrolysis cycle, causing a successive change in the packing efficiency of
each subcomplex (subcomplex I−γ, II−γ, or III−γ). The most important matter is
to retain the specific nonuniformity of the packing structure mentioned above.
43
ATP
>
>
ATP H 2 O
ADP, Pi
>
>
: β-subunit
Pi
Category (1)
Category (2)
Fig. 3.14 Order of packing efficiency for β subunit to which ATP• • •H 2 O (see the caption for
Fig. 3.6), ATP, ADP + Pi, nothing, or Pi is bound. For example, the packing efficiency (PE) of a
β subunit to which ATP• • •H 2 O is bound is higher than the PE to which ATP is bound and much
higher than the PE to which Pi is bound. We also define ATP(ATP• • •H 2 O) (not shown here) as
an intermediate between ATP and ATP• • •H 2 O. The PE of the β subunit with ATP(ATP• • •H 2 O)
bound is lower than that with ATP• • •H 2 O bound but higher than that with ATP bound. Categories
(1) and (2) are defined as follows: A β subunit to which ATP• • •H 2 O, ATP, or ADP + Pi is bound
falls into category (1) whereas a β subunit to which nothing or Pi is bound falls into category (2)
(2) The packing efficiency of subcomplex I−γ, II−γ, or III−γ (i.e., the packing
structure of the α 3 β 3 complex) is determined in accordance with that of the β
subunit included in it. That is, as corroborated by our theoretical analyses, when
the packing efficiency for a β subunit follows the order, “β subunit in subcomplex
I−γ” < “β subunit in subcomplex II−γ” < “β subunit in subcomplex III−γ”,
the packing efficiency for a subcomplex follows the order, “subcomplex I−γ”
< “subcomplex II−γ” < “subcomplex III−γ”.
(3) The orientation of the γ subunit is optimized in response to the packing structure
of the α 3 β 3 complex. The retainment of the highly stabilized β DP −γ and α E −γ
contacts is especially important.
The packing structure of the α 3 β 3 γ complex possessing the specific nonuniformity
shown in Fig. 3.11 is highly stable in terms of the water entropy. Here, we define
categories (1) and (2) as indicated in Fig. 3.14. A β subunit to which ATP• • •H 2 O,
ATP, or ADP + Pi is bound falls into category (1) whereas a β subunit to which
nothing or Pi is bound falls into category (2). For the retainment of the high stability,
at least it is required that two of the three β subunits be in category (1) and the other β
subunit be in category (2). The α 3 β 3 γ complex is involved in the ATP hydrolysis cycle
during which the chemical compound bound to each β subunit (i.e., ATP• • •H 2 O,
ATP, ADP + Pi, nothing, or Pi) successively changes. Since the packing efficiency of
a β subunit is strongly dependent on the chemical compound bound to it as depicted
in Fig. 3.14, the packing efficiency of each β subunit successively changes during
the ATP hydrolysis cycle, causing a successive change in the packing efficiency of
each subcomplex (subcomplex I−γ, II−γ, or III−γ). The most important matter is
to retain the specific nonuniformity of the packing structure mentioned above.