TY - JOUR
T1 - Phalloidin affects the myosin-dependent sliding velocities of actin filaments in a bound-divalent cation dependent manner
AU - Tokuraku, Kiyotaka
AU - Uyeda, Taro Q.P.
N1 - Funding Information:
We thank Mr Leonardo Mendoza for reading the manuscript. This work is supported by Japan Science and Technology Corporation and a Grants-in-Aid to T. U. from the Ministry of Education, Science, Culture of Japan.
PY - 2001
Y1 - 2001
N2 - We examined sliding velocities in vitro of four types of actin filaments, that is, filaments with Ca 2+ or Mg 2+ bound at the high affinity metal binding site, each with rhodamine phalloidin bound with a high or low stoichiometry. When surfaces coated with a high density of heavy meromyosin (HMM) were used, high stoichiometric concentrations of rhodamine phalloidin reduced sliding velocities of only Ca 2+-actin filaments, by 40%. As the HMM density on surfaces was reduced, continuous movement of actin filaments became dependent on the presence of methylcellulose and sliding velocities of all four types became progressively slower. Interestingly, Ca 2+-actin filaments with a high stoichiometric concentration of rhodamine phalloidin were the fastest among the four types of filaments on sparse HMM surfaces. In contrast, phalloidin did not affect steady state ATPase activities of HMM in the presence of Ca 2+- or Mg 2+-actin filaments. We speculate that the reversal of the order of sliding velocities among the four types of actin filaments between high and low densities of HMM relates with different axial elasticity of the actin filaments, so that stiffer filaments move slower on dense HMM surfaces, but faster on sparse surfaces, than elastic ones.
AB - We examined sliding velocities in vitro of four types of actin filaments, that is, filaments with Ca 2+ or Mg 2+ bound at the high affinity metal binding site, each with rhodamine phalloidin bound with a high or low stoichiometry. When surfaces coated with a high density of heavy meromyosin (HMM) were used, high stoichiometric concentrations of rhodamine phalloidin reduced sliding velocities of only Ca 2+-actin filaments, by 40%. As the HMM density on surfaces was reduced, continuous movement of actin filaments became dependent on the presence of methylcellulose and sliding velocities of all four types became progressively slower. Interestingly, Ca 2+-actin filaments with a high stoichiometric concentration of rhodamine phalloidin were the fastest among the four types of filaments on sparse HMM surfaces. In contrast, phalloidin did not affect steady state ATPase activities of HMM in the presence of Ca 2+- or Mg 2+-actin filaments. We speculate that the reversal of the order of sliding velocities among the four types of actin filaments between high and low densities of HMM relates with different axial elasticity of the actin filaments, so that stiffer filaments move slower on dense HMM surfaces, but faster on sparse surfaces, than elastic ones.
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U2 - 10.1023/A:1013120127602
DO - 10.1023/A:1013120127602
M3 - Article
C2 - 11808777
AN - SCOPUS:0035677405
VL - 22
SP - 371
EP - 378
JO - Journal of Muscle Research and Cell Motility
JF - Journal of Muscle Research and Cell Motility
SN - 0142-4319
IS - 4
ER -