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PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
4
pubmed:dateCreated
1992-5-28
pubmed:abstractText
The effect of temperature on the velocity of rhodamine phalloidin-labelled F-actin moving in vitro on rabbit skeletal myosin has been studied. Translating actin filaments were visualized by epi-fluorescence in an inverted microscope, equipped with temperature control (+/- 0.2 K) of the stage and objective. Images were recorded in real time at magnifications of 400x or 160x by an intensified CCD camera on video tape. Motion of individual filaments was tracked by hand and velocities determined using frame times recorded simultaneously on the video tape. Velocity changed from 12 microns per second at 42 degrees C to 11 nm per second at 3 degrees C. The Arrhenius plot is non-linear, with the data following a cubic regression curve with no evident breaks or jumps. Data taken over the temperature range from single preparations followed the same curve for both heating and cooling; this indicates reversibility and absence of hysteresis. A hyperbolic model that smoothly translates with temperature between two asymptotic activation energies fits the data above 7 degrees C: these energies are 50(+/- 5) kJ per mole (Q10 = 1.9) at high temperatures and 289(+/- 29) kJ per mole (Q10 = 76.5) at low temperature with a transition temperature of 15.4(+/- 0.6) degrees C. These values are compared with other measurements made in vitro, in solution studies and on muscle fibres. An Arrhenius activation energy of 50 kJ per mole and a transition temperature of 15 degrees C are consistent with previous determinations but 289 kJ per mole is significantly greater than has been seen at low temperatures in other systems. This may indicate a different rate-limiting step in the kinetics of skeletal myosin driving actin filaments in vitro below 15 degrees C. Current determinations of the myosin "step-size" assume that the actin velocity is determined by the rate of ATP hydrolysis; the data confirm similar activation energies above 20 degrees C but they show that the temperature dependencies and activation energies are different at lower temperatures, implying uncoupling of the two processes.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0022-2836
pubmed:author
pubmed:issnType
Print
pubmed:day
20
pubmed:volume
224
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
1029-38
pubmed:dateRevised
2009-11-19
pubmed:meshHeading
pubmed:year
1992
pubmed:articleTitle
Temperature dependence and Arrhenius activation energy of F-actin velocity generated in vitro by skeletal myosin.
pubmed:affiliation
National Institute for Medical Research, London, United Kingdom.
pubmed:publicationType
Journal Article, In Vitro, Research Support, Non-U.S. Gov't