Benjamin de Haas explains individual differences in eye movement patterns.
New Research In
Physical Sciences
Featured Portals
Articles by Topic
Biological Sciences
Featured Portals
Articles by Topic
-
Edited by Edwin W. Taylor, Northwestern University Feinberg School of Medicine, Chicago, IL, and approved October 25, 2005 (received for review June 23, 2005)
Abstract
Although the steps for the forward reaction of ATP hydrolysis by the motor protein kinesin have been studied extensively, the rates for the reverse reactions and thus the energy changes at each step are not as well defined. Oxygen isotopic exchange between water and Pi was used to evaluate the reverse rates. The fraction of the kinesin·ADP·Pi complex that reverts to ATP before release of Pi during net hydrolysis was ≈0 and ≈2.6% in the absence and presence of microtubules (MTs), respectively. The rate of synthesis of bound ATP from free Pi and the MT·kinesin·ADP complex was ≈1.7 M–1·s–1 (K 0.5 ADP = 70 μM) with monomeric kinesin in the absence of net hydrolysis. Synthesis of bound ATP from the ADP of the tethered head of a dimer–MT complex was 20-fold faster than for the monomer–MT complex. This MT-activated ATP synthesis at the tethered head is in marked contrast to the lack of MT stimulation of ADP release from the same site. The more rapid ATP synthesis with dimers suggests that the tethered head binds behind the strongly attached head, because this positions the neck linker of the tethered head toward the plus end of the MT and would thus facilitate its docking on synthesis of ATP. The observed rate of ATP synthesis also puts limits on the overall energetics that suggest that a significant fraction of the free energy of ATP hydrolysis is available to drive the docking of the neck linker on binding of ATP.
Footnotes
-
↵ * E-mail: ddh{at}andrew.cmu.edu.
-
Author contributions: D.D.H. designed and performed research.
-
Conflict of interest statement: No conflicts declared.
-
This paper was submitted directly (Track II) to the PNAS office.
-
Abbreviations: P c, partition coefficient; MT, microtubule; NL, neck linker.
- Copyright © 2005, The National Academy of Sciences
- David D. Hackney *
-
Edited by Edwin W. Taylor, Northwestern University Feinberg School of Medicine, Chicago, IL, and approved October 25, 2005 (received for review June 23, 2005)
Abstract
Although the steps for the forward reaction of ATP hydrolysis by the motor protein kinesin have been studied extensively, the rates for the reverse reactions and thus the energy changes at each step are not as well defined. Oxygen isotopic exchange between water and Pi was used to evaluate the reverse rates. The fraction of the kinesin·ADP·Pi complex that reverts to ATP before release of Pi during net hydrolysis was ≈0 and ≈2.6% in the absence and presence of microtubules (MTs), respectively. The rate of synthesis of bound ATP from free Pi and the MT·kinesin·ADP complex was ≈1.7 M–1·s–1 (K 0.5 ADP = 70 μM) with monomeric kinesin in the absence of net hydrolysis. Synthesis of bound ATP from the ADP of the tethered head of a dimer–MT complex was 20-fold faster than for the monomer–MT complex. This MT-activated ATP synthesis at the tethered head is in marked contrast to the lack of MT stimulation of ADP release from the same site. The more rapid ATP synthesis with dimers suggests that the tethered head binds behind the strongly attached head, because this positions the neck linker of the tethered head toward the plus end of the MT and would thus facilitate its docking on synthesis of ATP. The observed rate of ATP synthesis also puts limits on the overall energetics that suggest that a significant fraction of the free energy of ATP hydrolysis is available to drive the docking of the neck linker on binding of ATP.
- ATPase
- energy coupling
- motility
- motor protein
- isotopic exchange
Footnotes
-
↵ * E-mail: ddh{at}andrew.cmu.edu.
-
Author contributions: D.D.H. designed and performed research.
-
Conflict of interest statement: No conflicts declared.
-
This paper was submitted directly (Track II) to the PNAS office.
-
Abbreviations: P c, partition coefficient; MT, microtubule; NL, neck linker.
- Copyright © 2005, The National Academy of Sciences
The tethered motor domain of a kinesin-microtubule complex catalyzes reversible synthesis of bound ATP
Sign up for Article Alerts
Jump to section
You May Also be Interested in
The distant rock has offered clues about planet formation and the state of the early solar system.
Image credit: Wikimedia Commons/NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/ESA.
Researchers report negative emotional contagion, or the coordination of emotional states between multiple individuals, in common ravens, suggesting convergent emotional evolution in birds and mammals.
Image courtesy of Jessie E. C. Adriaense.
A study examines trends in global fishing fleets and finds that by 2015, 68% of the global fishing fleet became motorized, and that the overall number of fleet vessels increased to 3.7 million, despite a consistent decrease in the catch per unit of effort.
Image courtesy of Pixabay/3282700.
A method to determine gender from fingerprints suggests pottery making was not a primarily female activity in ancient Puebloan society, challenging previous assumptions about gendered divisions of labor in ancient societies.
Image courtesy of John Kantner.