Substoichiometric concentrations of ATP-G-actin are required to anneal actin polymerized by calcium ions.
At 3 degrees C and pH 7.0, the addition of 40 nM ATP-G-actin to F-actin (12 microM as the monomer), polymerized in the presence of 4 mM CaCl2, determines a substantial and rapid increase of the viscosity of the solution, which is accompanied by the incorporation of the ATP-G-actin added into the polymer. The hypothesis that the presence of ATP-actin at the filament end(s) promotes the annealing reaction is substantiated by the finding that, after the addition of ATP-G-actin, the average filament length is increased. This finding is relevant, not only because it provides evidences in favour of the existence of annealing but also because it shows that the concentration of ATP-G-actin influences the filaments length distribution through a mechanism different from the elongation reaction.
Grazi
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Istituto di Chimica Biologica, Università di Ferrara, Italy.
Trombetta
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G
Rizzieri
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Guidoboni
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M
D000199:Actins / Q000494:pharmacology*; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D009132:Muscles / Q000032:analysis; D011108:Polymers; D011817:Rabbits; D012996:Solutions; D013050:Spectrometry, Fluorescence; D014783:Viscosity
C022920:ATP-G-actin; D000199:Actins; D011108:Polymers; D012996:Solutions; D000255:Adenosine Triphosphate; D002122:Calcium Chloride