Opinion: To advance sustainable stewardship, we must document not only biodiversity but geodiversity
Key abiotic features and processes should be incorporated into policy documents.
Image credit: Shutterstock/1968.
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 advent of the approach has proven to be a boon for researchers, offering evidence of geophysical processes previously only theorized.
Image credit: Suzan van der Lee (Northwestern University, Evanston, IL).
Researchers report a marine ammonite from the Cretaceous Period preserved in Burmese amber from Myanmar, and the rare specimen in amber warrants exploration of the possibly exceptional circumstances of its fossilization.
Image courtesy of Bo Wang.
Exposure to low humidity makes mice infected with influenza more susceptible to severe disease by impairing airway tissue repair and innate antiviral defense, suggesting that controlling humidity may help curb influenza during winter.
Image courtesy of Pixabay/qimono.
A study suggests a potential biomarker, the metabotropic glutamatergic receptor 5, for intervention and suicide risk management in posttraumatic stress disorder (PTSD).
Image courtesy of Margaret T. Davis and Irina Esterlis.