1. Mechanism for oscillatory assembly of microtubules
- Author
-
Michael Caplow and John Shanks
- Subjects
Periodicity ,Protein subunit ,Population ,Side reaction ,macromolecular substances ,In Vitro Techniques ,Biochemistry ,Guanosine Diphosphate ,Microtubules ,Dissociation (chemistry) ,Microtubule ,Tubulin ,Animals ,education ,Molecular Biology ,High concentration ,education.field_of_study ,biology ,Chemistry ,Brain ,Cell Biology ,Molecular Weight ,Kinetics ,Polymerization ,biology.protein ,Biophysics ,Cattle ,Guanosine Triphosphate ,Protein Binding - Abstract
Dampened oscillations of microtubule assembly can accompany polymerization at high tubulin subunit concentrations. This presumably results from a synchronization of dynamic instability behavior, which generates a large population of rapidly disassembling microtubules, that liberate tubulin-GDP oligomers. Subunits in oligomers cannot assemble until they dissociate, to allow GDP-GTP exchange. To determine whether rapidly disassembling microtubules generate oligomers directly, we measured the rate of dilution-induced disassembly of tubulin-GDP microtubules and the rate of dissociation of GDP from the so-formed tubulin-GDP subunits. The rate of GDP dissociation from liberated subunits was found to correspond to that of tubulin-GDP subunits (t1/2 = 5 s), rather than tubulin-GDP oligomers. This indicates that tubulin-GDP subunits are released from microtubules undergoing rapid disassembly. Oligomers apparently form in a side reaction from the high concentration of tubulin-GDP subunits liberated from the synchronously disassembling microtubule population. The rate of subunit dissociation is 0.11 s-1 with oligomers formed by concentrating tubulin-GDP subunits and 0.045 s-1 with oligomers formed by cold-induced microtubule disassembly. This difference provides evidence that the conformation of tubulin-GDP subunits released from rapidly disassembling microtubules differs from tubulin-GDP subunits that were not recently in the microtubule lattice.
- Published
- 1990