Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.4.4 (kinesin)
 5,033 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Kinesin is a motor protein that uses the energy derived from ATP hydrolysis to transport organelles along microtubules. By analyzing the thermal fluctuation of microtubules tethered to glass surfaces by single molecules of kinesin, we have measured the torsional flexibility of the motor protein. The torsional stiffness of kinesin, (117 +/- 19) x 10(-24) N.m.rad-1 (mean +/- SEM), is so low that one kT of energy (approximately 4.1 x 10(-21) J at room temperature) is sufficient to twist a kinesin molecule through more than 360 degrees from its resting orientation. Consistent with this flexibility, motility assays show that one or more kinesin molecules can move a microtubule equally well in any direction. These results explain how a motor on the surface of an organelle can rapidly bind to and capture a microtubule irrespective of the organelle's orientation. Furthermore, the flexibility ensures that several motors can efficiently work together even though they are randomly oriented on the surface of an organelle rather than being in precise arrays like the motors of muscle and cilia.
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PMID:Kinesin swivels to permit microtubule movement in any direction. 826 3

Kinesin-1 is a motor protein that carries cellular cargo such as membrane-bounded organelles along microtubules (MTs). The homodimeric motor molecule contains two N-terminal motor domains (the motor "heads"), a long coiled-coil domain (the "rod" or "stalk"), and two small globular "tail" domains. Much has been learned about how kinesin's heads step along a MT and how the tail is involved in cargo binding and autoinhibition. However, little is known about the role of the rod. Here, we investigate the extension of the rod during active transport by measuring the height at which MTs glide over a kinesin-coated surface in the presence of ATP. To perform height measurements with nanometer precision, we used fluorescence interference contrast microscopy, which is based on the self-interference of fluorescent light from objects near a reflecting surface. Using an in situ calibrating method, we determined that kinesin-1 molecules elevate gliding MTs 17 +/- 2 nm (mean +/- SEM) above the surface. When varying the composition of the surrounding nucleotides or removing the negatively charged -COOH termini of the MTs by subtilisin digestion, we found no significant changes in the measured distance. Even though this distance is significantly shorter than the contour length of the motor molecule ( approximately 60 nm), it may be sufficient to prevent proteins bound to the MTs or prevent the organelles from interfering with transport.
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PMID:The distance that kinesin-1 holds its cargo from the microtubule surface measured by fluorescence interference contrast microscopy. 1703 6

The fundamental biophysics of gliding microtubule (MT) motility by surface-tethered kinesin-1 motor proteins has been widely studied, as well as applied to capture and transport analytes in bioanalytical microdevices. In these systems, phenomena such as molecular wear and fracture into shorter MTs have been reported due the mechanical forces applied on the MT during transport. In the present work, we show that MTs can be split longitudinally into protofilament bundles (PFBs) by the work performed by surface-bound kinesin motors. We examine the properties of these PFBs using several techniques (e.g., fluorescence microscopy, SEM, AFM), and show that the PFBs continue to be mobile on the surface and display very high curvature compared to MT. Further, higher surface density of kinesin motors and shorter kinesin-surface tethers promote PFB formation, whereas modifying MT with GMPCPP or higher paclitaxel concentrations did not affect PFB formation.
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PMID:Mechanical splitting of microtubules into protofilament bundles by surface-bound kinesin-1. 2800 Jul 14