Neurotubule assembly at substoichiometric nucleotide levels using a GTP regenerating system |
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Authors: | Robert K MacNeal Bradford C Webb Daniel L Purich |
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Institution: | Department of Chemistry, University of California Santa Barbara, California 93106 USA |
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Abstract: | Tubulin derived from cold depolymerized bovine microtubules has been gel filtered to obtain a tubulin preparation with only 3% of the tubulin dimers containing exchangeable 3H]-guanine nucleotide. In the presence of acetyl-P and bacterial acetate kinase, this preparation polymerizes to form microtubules which are morphologically indistinguishable from microtubules formed in the presence of excess GTP. The extent of microtubule formation at substoichiometric nucleotide levels using the GTP regenerating system exceeds the extent of assembly obtained with excess GTP. It is concluded that the exchangeable guanine nucleotide site can be virtually unoccupied in intact neurotubules and this finding indicates that GDP can “catalyze” tubule assembly in the presence of a GTP regenerating system. |
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Keywords: | To whom inquiries regarding this report should be addressed |
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