These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: The rate-limiting step in the actomyosin adenosinetriphosphatase cycle.
    Author: Stein LA, Chock PB, Eisenberg E.
    Journal: Biochemistry; 1984 Mar 27; 23(7):1555-63. PubMed ID: 6232948.
    Abstract:
    We have previously shown that myosin does not have to detach from actin during each cycle of ATP hydrolysis. In the present study, using the A-1 isoenzyme of myosin subfragment 1, we have investigated the nature of the rate-limiting steps in the ATPase cycle. Our results show that, at 15 degrees C, at very low ionic strength, KATPase determined from the double-reciprocal plot of ATPase activity vs. actin concentration is more than 6-fold stronger than KBINDING determined by directly measuring the binding of A-1 myosin subfragment 1 to actin during steady-state ATP hydrolysis. Computer modeling shows that this large difference between KATPase and KBINDING is not compatible with Pi release being the rate-limiting step in the ATPase cycle. If Pi release is not rate limiting, it is possible that the ATP hydrolysis step, itself, is rate limiting. However, this predicts that, at high actin concentration, the value of the initial Pi burst should be close to zero. Therefore, we measured the magnitude of the initial Pi burst in the presence of actin, using both direct measurement and measurement of relative fluorescence magnitude. Our results suggest that the magnitude of the initial Pi burst in the presence of actin is considerably higher than would be expected if the ATP hydrolysis step were the rate-limiting step in the ATPase cycle.(ABSTRACT TRUNCATED AT 250 WORDS)
    [Abstract] [Full Text] [Related] [New Search]