Okuno, Makoto (1980) Inhibition and relaxation of sea urchin sperm flagella by vanadate. Journal of Cell Biology, 85 (3). pp. 712-725. ISSN 0021-9525. http://resolver.caltech.edu/CaltechAUTHORS:OKUjcb80
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Direct measurements of the stiffness (elastic bending resistance) of demembranated sera urchin sperm flagella were made in the presence of MgATP2- and vanadate. Under these conditions, the flagellum is in a relaxed state, with a stiffness of approximately 0.9 x 10^(-21) N m^2, which is approximately 5% of the stiffness obtained in the rigor state in the absence of MgATP2-. MgADP- dose not substitute for MgATP2- in producing relaxed state. A progressive inhibition of movement is observed after addition of MgATP2- to flagella preincubated with vanadate, in which new bend generation, propagation, and relaxation by straightening are distinguished, depending on the ratio of MgATP2- and vanadate. At appropriate concentrations of vanadate, increase of the velocity of bend propagation is observed at a very low concentration of MgATP2- that is not enough to induce spontaneous beating. Vanadate enhances competitive inhibition of beat frequency by MgADP- but not by ADP3-, ATP4-, or Pi. These observations, and the uncompetitive inhibition of beat frequency by vanadate, indicate that vanadate can only bind to dynein-nucleotide complexes induced by MgATP2- and MgADP-. The state accessible by MgATP2- binding must be a state in which the cross-bridges are detached and the flagellum is relaxed. The state accessible by MgADP- binding must be a cross-bridged state. Bound vanadate prevents the transition between these two states. Inhibition and relaxation by vanadate in the presence of MgATP2- results from the specific affinity of vanadate for a state in which nucleotide is bound, rather than a specific affinity for the detached state.
|Additional Information:||Copyright © 1980 by The Rockefeller University Press. Received for publication 27 August 1979, and in revised form 28 January 1980. The author is indebted to Professor C.J. Brokaw for the opportunity to work in his laboratory and for valuable discussion and kind help in preparation of the manuscript. He thanks also T.F. Simonick for able assistance during the experiments. This work was supported by National Institutes of Health grant GM 18711 to C.J. Brokaw.|
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|Deposited On:||17 Apr 2008|
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