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Roles of nucleoside triphosphates in microtubule assembly
Abstract:
Depolymerization of microtubules in the ATP-reassembly buffer permitted the preparation of GDPETNGTP. Incubation of this tubulin fraction at 35 degrees with ATP induced the phosphorylation of E-site GDP into GTP, which was then dephosphorylated during microtubule assembly. Incubation of GDPETNGTP with phosphoenolpyruvate and pyruvate kinase [EC 2.7.1.40] also induced polymerization. Depolymerization of microtubules in the GTP-reassembly buffer yielded GTPETNGTP, which was capable of polymerizing into microtubules even in the absence of free GTP. In the presence of 4 M glycerol, GDPETNGTP assembled into microtubules with no change in the bound nucleotides.
Insights
Tubulin nucleotide exchange was studied. GDP-tubulin can be converted to GTP-tubulin, enabling microtubule assembly and demonstrating nucleotide-dependent polymerization dynamics.
Area of Science:
- Biochemistry
- Cell Biology
- Structural Biology
Background:
- Microtubules are essential cytoskeletal components involved in various cellular processes.
- Tubulin, the subunit of microtubules, binds to GTP, which is crucial for polymerization.
Purpose of the Study:
- To investigate the nucleotide exchange dynamics of tubulin.
- To understand the role of GDP-tubulin and GTP-tubulin in microtubule assembly.
Main Methods:
- Tubulin depolymerization in ATP- and GTP-reassembly buffers.
- Incubation of tubulin fractions with ATP, phosphoenolpyruvate, and pyruvate kinase.
- Monitoring tubulin polymerization under various nucleotide conditions.
Main Results:
- GDP-tubulin could be phosphorylated to GTP-tubulin, initiating polymerization.
- GTP-tubulin, prepared via depolymerization in GTP buffer, polymerized independently of free GTP.
- GDP-tubulin-GTP (GDPETNGTP) assembled into microtubules without altering bound nucleotides in the presence of glycerol.
Conclusions:
- Tubulin nucleotide state is a key regulator of microtubule assembly.
- GDP-tubulin can serve as a precursor for GTP-tubulin, highlighting a pathway for nucleotide conversion.
- The study provides insights into the biochemical mechanisms governing microtubule dynamics.