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Importance of water entropy in rotation mechanism of F 1 -ATPase

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ABSTRACT

We briefly review our theoretical study on the rotation scheme of F1-ATPase. In the scheme, the key factor is the water entropy which has been shown to drive a variety of self-assembly processes in biological systems. We decompose the crystal structure of F1-ATPase into three sub-complexes each of which is composed of the γ subunit, one of the β subunits, and two α subunits adjacent to them. The βE, βTP, and βDP subunits are involved in the sub-complexes I, II, and III, respectively. We calculate the hydration entropy of each sub-complex using a hybrid of the integral equation theory for molecular liquids and the morphometric approach. It is found that the absolute value of the hydration entropy follows the order, sub-complex I > sub-complex II > sub-complex III. Moreover, the differences are quite large, which manifests highly asymmetrical packing of F1-ATPase. In our picture, this asymmetrical packing plays crucially important roles in the rotation of the γ subunit. We discuss how the rotation is induced by the water-entropy effect coupled with such chemical processes as ATP binding, ATP hydrolysis, and release of the products.

No MeSH data available.


Schematic representation of the generation of the three sub-complexes from the crystal structure.
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f5-7_113: Schematic representation of the generation of the three sub-complexes from the crystal structure.

Mentions: We name the sub-complexes in terms of their positions in the crystal structure. For example, when the γ subunit rotates by 120° (see Fig. 3(c)), the arrangement changes and sub-complex III now comprises γ, βE, αE, and αTP. We first generate the three sub-complexes from the crystal structure (see Fig. 5) and then calculate the HE of each sub-complex. To make the number of the atoms in each sub-complex impartial, we add the HE of ATP-Mg2+ to the HE of sub-complex I. The values of the HE of the three sub-complexes are shown in Table 1. It follows that the value of /S//kB (kB is the Boltzmann constant) is in the order, sub-complex III < sub-complex II < sub-complex I. Therefore, the water-entropy loss upon the insertion of sub-complex III is the smallest.


Importance of water entropy in rotation mechanism of F 1 -ATPase
Schematic representation of the generation of the three sub-complexes from the crystal structure.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC5036781&req=5

f5-7_113: Schematic representation of the generation of the three sub-complexes from the crystal structure.
Mentions: We name the sub-complexes in terms of their positions in the crystal structure. For example, when the γ subunit rotates by 120° (see Fig. 3(c)), the arrangement changes and sub-complex III now comprises γ, βE, αE, and αTP. We first generate the three sub-complexes from the crystal structure (see Fig. 5) and then calculate the HE of each sub-complex. To make the number of the atoms in each sub-complex impartial, we add the HE of ATP-Mg2+ to the HE of sub-complex I. The values of the HE of the three sub-complexes are shown in Table 1. It follows that the value of /S//kB (kB is the Boltzmann constant) is in the order, sub-complex III < sub-complex II < sub-complex I. Therefore, the water-entropy loss upon the insertion of sub-complex III is the smallest.

View Article: PubMed Central - PubMed

ABSTRACT

We briefly review our theoretical study on the rotation scheme of F1-ATPase. In the scheme, the key factor is the water entropy which has been shown to drive a variety of self-assembly processes in biological systems. We decompose the crystal structure of F1-ATPase into three sub-complexes each of which is composed of the &gamma; subunit, one of the &beta; subunits, and two &alpha; subunits adjacent to them. The &beta;E, &beta;TP, and &beta;DP subunits are involved in the sub-complexes I, II, and III, respectively. We calculate the hydration entropy of each sub-complex using a hybrid of the integral equation theory for molecular liquids and the morphometric approach. It is found that the absolute value of the hydration entropy follows the order, sub-complex I &gt; sub-complex II &gt; sub-complex III. Moreover, the differences are quite large, which manifests highly asymmetrical packing of F1-ATPase. In our picture, this asymmetrical packing plays crucially important roles in the rotation of the &gamma; subunit. We discuss how the rotation is induced by the water-entropy effect coupled with such chemical processes as ATP binding, ATP hydrolysis, and release of the products.

No MeSH data available.