Rotation scheme of V1-motor is different from that of F1-motor.
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ABSTRACT:
SUBMITTER: Imamura H
PROVIDER: S-EPMC1306795 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The chloroplast-type F(1) ATPase is the key enzyme of energy conversion in chloroplasts, and is regulated by the endogenous inhibitor epsilon, tightly bound ADP, the membrane potential and the redox state of the gamma subunit. In order to understand the molecular mechanism of epsilon inhibition, we constructed an expression system for the alpha(3)beta(3)gamma subcomplex in thermophilic cyanobacteria allowing thorough investigation of epsilon inhibition. epsilon Inhibition was found to be ATP-independent, and different to that observed for bacterial F(1)-ATPase. The role of the additional region on the gamma subunit of chloroplast-type F(1)-ATPase in epsilon inhibition was also determined. By single molecule rotation analysis, we succeeded in assigning the pausing angular position of gamma in epsilon inhibition, which was found to be identical to that observed for ATP hydrolysis, product release and ADP inhibition, but distinctly different from the waiting position for ATP binding. These results suggest that the epsilon subunit of chloroplast-type ATP synthase plays an important regulator for the rotary motor enzyme, thus preventing wasteful ATP hydrolysis.
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Project description:F1-ATPase, the catalytic complex of the ATP synthase, is a molecular motor that can consume ATP to drive rotation of the ?-subunit inside the ring of three ??-subunit heterodimers in 120° power strokes. To elucidate the mechanism of ATPase-powered rotation, we determined the angular velocity as a function of rotational position from single-molecule data collected at 200,000 frames per second with unprecedented signal-to-noise. Power stroke rotation is more complex than previously understood. This paper reports the unexpected discovery that a series of angular accelerations and decelerations occur during the power stroke. The decreases in angular velocity that occurred with the lower-affinity substrate ITP, which could not be explained by an increase in substrate-binding dwells, provides direct evidence that rotation depends on substrate binding affinity. The presence of elevated ADP concentrations not only increased dwells at 35° from the catalytic dwell consistent with competitive product inhibition but also decreased the angular velocity from 85° to 120°, indicating that ADP can remain bound to the catalytic site where product release occurs for the duration of the power stroke. The angular velocity profile also supports a model in which rotation is powered by Van der Waals repulsive forces during the final 85° of rotation, consistent with a transition from F1 structures 2HLD1 and 1H8E (Protein Data Bank).
| S-EPMC3956197 | biostudies-literature
Project description:F1, a water-soluble portion of FoF1-ATP synthase, is an ATP hydrolysis-driven rotary motor. The central gamma-subunit rotates in the alpha 3 beta 3 cylinder by repeating the following four stages of rotation: ATP-binding dwell, rapid 80 degrees substep rotation, interim dwell, and rapid 40 degrees substep rotation. At least two 1-ms catalytic events occur in the interim dwell, but it is still unclear which steps in the ATPase cycle, except for ATP binding, correspond to these events. To discover which steps, we analyzed rotations of F1 subcomplex (alpha 3 beta 3 gamma) from thermophilic Bacillus PS3 under conditions where cleavage of ATP at the catalytic site is decelerated: hydrolysis of ATP by the catalytic-site mutant F1 and hydrolysis of a slowly hydrolyzable substrate ATP gamma S (adenosine 5'-[gamma-thio]triphosphate) by wild-type F1. In both cases, interim dwells were extended as expected from bulk phase kinetics, confirming that cleavage of ATP takes place during the interim dwell. Furthermore, the results of ATP gamma S hydrolysis by the mutant F1 ensure that cleavage of ATP most likely corresponds to one of the two 1-ms events and not some other faster undetected event. Thus, cleavage of ATP on F1 occurs in 1 ms during the interim dwell, and we call this interim dwell catalytic dwell.
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Project description:A novel method for detecting F(1)-ATPase rotation in a manner sufficiently sensitive to achieve acquisition rates with a time resolution of 2.5 micros (equivalent to 400,000 fps) is reported. This is sufficient for resolving the rate at which the gamma-subunit travels from one dwell state to another (transition time). Rotation is detected via a gold nanorod attached to the rotating gamma-subunit of an immobilized F(1)-ATPase. Variations in scattered light intensity allow precise measurement of changes in the angular position of the rod below the diffraction limit of light. Using this approach, the transition time of Escherichia coli F(1)-ATPase gamma-subunit rotation was determined to be 7.62 +/- 0.15 (standard deviation) rad/ms. The average rate-limiting dwell time between rotation events observed at the saturating substrate concentration was 8.03 ms, comparable to the observed Mg(2+)-ATPase k(cat) of 130 s(-)(1) (7.7 ms). Histograms of scattered light intensity from ATP-dependent nanorod rotation as a function of polarization angle allowed the determination of the nanorod orientation with respect to the axis of rotation and plane of polarization. This information allowed the drag coefficient to be determined, which implied that the instantaneous torque generated by F(1) was 63.3 +/- 2.9 pN nm. The high temporal resolution of rotation allowed the measurement of the instantaneous torque of F(1), resulting in direct implications for its rotational mechanism.
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Project description: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 ? subunit, one of the ? subunits, and two ? subunits adjacent to them. The ?E, ?TP, and ?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 > 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 ? 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.
| S-EPMC5036781 | biostudies-literature
Project description:Rotary ATPases are unique rotary molecular motors that function as energy conversion machines. Among all known rotary ATPases, F1-ATPase is the best characterized rotary molecular motor. There are many high-resolution crystal structures and the rotation dynamics have been investigated in detail by extensive single-molecule studies. In contrast, knowledge on the structure and rotation dynamics of V1-ATPase, another rotary ATPase, has been limited. However, recent high-resolution structural studies and single-molecule studies on V1-ATPase have provided new insights on how the catalytic sites in this molecular motor change its conformation during rotation driven by ATP hydrolysis. In this review, we summarize recent information on the structural features and rotary dynamics of V1-ATPase revealed from structural and single-molecule approaches and discuss the possible chemomechanical coupling scheme of V1-ATPase with a focus on differences between rotary molecular motors.
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Project description:F(O)F(1)-ATP synthases are ubiquitous proton- or ion-powered membrane enzymes providing ATP for all kinds of cellular processes. The mechanochemistry of catalysis is driven by two rotary nanomotors coupled within the enzyme. Their different step sizes have been observed by single-molecule microscopy including videomicroscopy of fluctuating nanobeads attached to single enzymes and single-molecule Förster resonance energy transfer. Here we review recent developments of approaches to monitor the step size of subunit rotation and the transient elastic energy storage mechanism in single F(O)F(1)-ATP synthases.
| S-EPMC3538427 | biostudies-literature
Project description:V1-ATPase is an ATP-driven rotary motor that is composed of a ring-shaped A3B3 complex and a central DF shaft. The nucleotide-free A3B3 complex of Enterococcus hirae, composed of three identical A1B1 heterodimers, showed a unique asymmetrical structure, probably due to the strong binding of the N-terminal barrel domain, which forms a crown structure. Here, we mutated the barrel region to weaken the crown, and performed structural analyses using high-speed atomic force microscopy and x-ray crystallography of the mutant A3B3. The nucleotide-free mutant A3B3 complex had a more symmetrical open structure than the wild type. Binding of nucleotides produced a closely packed spiral-like structure with a disrupted crown. These findings suggest that wild-type A3B3 forms a metastable (stressed) asymmetric structure composed of unstable A1B1 conformers due to the strong constraint of the crown. The results further the understanding of the principle of the cooperative transition mechanism of rotary motors.
| S-EPMC6353620 | biostudies-literature
Project description:Despite extensive studies, the structural basis for the mechanochemical coupling in the rotary molecular motor F1-ATPase (F1) is still incomplete. We performed single-molecule FRET measurements to monitor conformational changes in the stator ring-?3?3, while simultaneously monitoring rotations of the central shaft-?. In the ATP waiting dwell, two of three ?-subunits simultaneously adopt low FRET nonclosed forms. By contrast, in the catalytic intermediate dwell, two ?-subunits are simultaneously in a high FRET closed form. These differences allow us to assign crystal structures directly to both major dwell states, thus resolving a long-standing issue and establishing a firm connection between F1 structure and the rotation angle of the motor. Remarkably, a structure of F1 in an ?-inhibited state is consistent with the unique FRET signature of the ATP waiting dwell, while most crystal structures capture the structure in the catalytic dwell. Principal component analysis of the available crystal structures further clarifies the five-step conformational transitions of the ??-dimer in the ATPase cycle, highlighting the two dominant modes: the opening/closing motions of ? and the loosening/tightening motions at the ??-interface. These results provide a new view of tripartite coupling among chemical reactions, stator conformations, and rotary angles in F1-ATPase.
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Project description:A rotary motor F(1), a catalytic part of ATP synthase, makes a 120 degrees step rotation driven by hydrolysis of one ATP, which consists of 80 degrees and 40 degrees substeps initiated by ATP binding and probably by ADP and/or P(i) dissociation, respectively. During active rotations, F(1) spontaneously fails in ADP release and pauses after a 80 degrees substep, which is called the ADP-inhibited form. In the present work, we found that, when pushed >+40 degrees with magnetic tweezers, the pausing F(1) resumes its active rotation after releasing inhibitory ADP. The rate constant of the mechanical activation exponentially increased with the pushed angle, implying that F(1) weakens the affinity of its catalytic site for ADP as the angle goes forward. This finding explains not only its unidirectional nature of rotation, but also its physiological function in ATP synthesis; it would readily bind ADP from solution when rotated backward by an F(o) motor in the ATP synthase. Furthermore, the mechanical work for the forced rotation was efficiently converted into work for expelling ADP from the catalytic site, supporting the tight coupling between the rotation and catalytic event.
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