Dataset Information

Structure of a fast kinesin: implications for ATPase mechanism and interactions with microtubules.

ABSTRACT: We determined the crystal structure of the motor domain of the fast fungal kinesin from Neurospora crassa (NcKin). The structure has several unique features. (i) Loop 11 in the switch 2 region is ordered and enables one to describe the complete nucleotide-binding pocket, including three inter-switch salt bridges between switch 1 and 2. (ii) Loop 9 in the switch 1 region bends outwards, making the nucleotide-binding pocket very wide. The displacement in switch 1 resembles that of the G-protein ras complexed with its guanosine nucleotide exchange factor. (iii) Loop 5 in the entrance to the nucleotide-binding pocket is remarkably long and interacts with the ribose of ATP. (iv) The linker and neck region is not well defined, indicating that it is mobile. (v) Image reconstructions of ice-embedded microtubules decorated with NcKin show that it interacts with several tubulin subunits, including a central beta-tubulin monomer and the two flanking alpha-tubulin monomers within the microtubule protofilament. Comparison of NcKin with other kinesins, myosin and G-proteins suggests that the rate-limiting step of ADP release is accelerated in the fungal kinesin and accounts for the unusually high velocity and ATPase activity.

SUBMITTER: Song YH

PROVIDER: S-EPMC125725 | biostudies-literature | 2001 Nov

REPOSITORIES: biostudies-literature

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Structure of a fast kinesin: implications for ATPase mechanism and interactions with microtubules.

Song Y H YH Marx A A Müller J J Woehlke G G Schliwa M M Krebs A A Hoenger A A Mandelkow E E

The EMBO journal 20011101 22

We determined the crystal structure of the motor domain of the fast fungal kinesin from Neurospora crassa (NcKin). The structure has several unique features. (i) Loop 11 in the switch 2 region is ordered and enables one to describe the complete nucleotide-binding pocket, including three inter-switch salt bridges between switch 1 and 2. (ii) Loop 9 in the switch 1 region bends outwards, making the nucleotide-binding pocket very wide. The displacement in switch 1 resembles that of the G-protein ra ...[more]

PMID: 11707393

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Project description:The transport of cytoplasmic components can be profoundly affected by hydrodynamics. Cytoplasmic streaming in Drosophila oocytes offers a striking example. Forces on fluid from kinesin-1 are initially directed by a disordered meshwork of microtubules, generating minor slow cytoplasmic flows. Subsequently, to mix incoming nurse cell cytoplasm with ooplasm, a subcortical layer of microtubules forms parallel arrays that support long-range, fast flows. To analyze the streaming mechanism, we combined observations of microtubule and organelle motions with detailed mathematical modeling. In the fast state, microtubules tethered to the cortex form a thin subcortical layer and undergo correlated sinusoidal bending. Organelles moving in flows along the arrays show velocities that are slow near the cortex and fast on the inward side of the subcortical microtubule layer. Starting with fundamental physical principles suggested by qualitative hypotheses, and with published values for microtubule stiffness, kinesin velocity, and cytoplasmic viscosity, we developed a quantitative coupled hydrodynamic model for streaming. The fully detailed mathematical model and its simulations identify key variables that can shift the system between disordered (slow) and ordered (fast) states. Measurements of array curvature, wave period, and the effects of diminished kinesin velocity on flow rates, as well as prior observations on f-actin perturbation, support the model. This establishes a concrete mechanistic framework for the ooplasmic streaming process. The self-organizing fast phase is a result of viscous drag on kinesin-driven cargoes that mediates equal and opposite forces on cytoplasmic fluid and on microtubules whose minus ends are tethered to the cortex. Fluid moves toward plus ends and microtubules are forced backward toward their minus ends, resulting in buckling. Under certain conditions, the buckling microtubules self-organize into parallel bending arrays, guiding varying directions for fast plus-end directed fluid flows that facilitate mixing in a low Reynolds number regime.

Dataset Information

Structure of a fast kinesin: implications for ATPase mechanism and interactions with microtubules.

Publications

Structure of a fast kinesin: implications for ATPase mechanism and interactions with microtubules.

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