Related Experiment Video
Updated: Aug 6, 2026
12:20
Preparation of Segmented Microtubules to Study Motions Driven by the Disassembling Microtubule Ends
Published on: March 16, 2014
The magnesium-GTP interaction in microtubule assembly
1Laboratory of Molecular Pharmacology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
European Journal of Biochemistry
|May 15, 1994
Summary
Magnesium ions (Mg2+) are crucial for microtubule assembly, playing a role beyond enhancing GTP binding to tubulin. This suggests Mg2+ may be catalytic or involved in nucleation during polymerization.
Area of Science:
- Biochemistry
- Cell Biology
- Structural Biology
Background:
- Microtubule assembly is fundamental for cellular processes.
- Tubulin polymerization involves the binding and hydrolysis of GTP.
- The role of magnesium ions (Mg2+) in this process is not fully understood.
Purpose of the Study:
- To investigate the specific role of Mg2+ in tubulin-GDP polymerization.
- To determine the relationship between Mg2+ concentration, GTP binding, and microtubule assembly.
- To elucidate Mg2+'s function beyond enhancing GTP exchange.
Main Methods:
- Studying tubulin-GDP assembly with varying Mg2+ and GTP concentrations.
- Utilizing EDTA to chelate Mg2+ and assess its impact.
- Quantifying GTP binding to tubulin-GDP.
- Measuring Mg2+ binding to tubulin-GDP and its changes during polymerization.
Main Results:
- Tubulin-GDP assembly occurs with low free Mg2+ (< 3 microM) and is inhibited by EDTA and high GTP.
- Mg2+ stimulates GTP binding to tubulin-GDP, but this stimulation is not directly proportional to reaction rates.
- The increase in Mg2+ bound to tubulin is substoichiometric to GTP bound.
- Mg2+ is lost from tubulin during GTP hydrolysis upon polymerization.
Conclusions:
- Mg2+ plays a critical role in tubulin assembly that is distinct from enhancing GTP binding.
- In trace amounts, Mg2+'s role may be catalytic during polymerization or limited to nucleation.
- Understanding Mg2+'s function is key to comprehending microtubule dynamics.
Related Concept Videos
02:17Microtubule Instability
Microtubules are hollow cylindrical filaments having a diameter of approximately 25 nm and a length that varies from 200 nm to 25 μm. GTP-bound tubulin subunits form αβ-heterodimers for microtubule assembly. These core building blocks interact longitudinally, polymerizing into protofilaments. The protofilaments then interact with one another through lateral bonding forces to form stable cylindrical microtubules. These cylindrical filaments are dynamic as they undergo repeated assembly and...
01:23Microtubule Formation
Microtubules are dynamic structures that undergo continuous assembly and disassembly. They originate from specialized multi-protein complexes known as microtubule organizing centers or MTOCs. Within the MTOC, the point of origin of the microtubule is known as the minus end, while the end radiating outward is the plus end. Microtubules serve two primary functions — the organization of spindle complexes to separate sister chromatids during mitotic or meiotic cell division and the formation of...
01:42Microtubule Associated Proteins (MAPs)
Microtubule function and architecture are regulated by an array of specialized proteins called microtubule-associated proteins or MAPs. These proteins are widespread across different organisms and have conserved protein motifs, like the multi-TOG domain for tubulin binding found in the CLASP family of MAPs. Some MAPs are lineage-specific based on their conserved domains. Their functions depend upon the cytoskeletal architecture and cell type they are located within. In-plant cells, a specific...
01:45Destabilization of Microtubules
The destabilization of microtubules can occur during different stages of the microtubule lifecycle, such as nucleation or elongation. It can take place at either end of the microtubule or in the microtubule lattices as a whole. The lifespan of individual microtubules within a cell varies according to the cell type and stage of the cell cycle. During interphase, the lifespan of the microtubule is about 30 minutes, while during cell division, it is about 15 minutes. In axonal microtubules of...
01:32Assembly of Complex Microtubule Structures
Complex microtubule structures are present in resting cells and in dividing cells. In resting cells, they are responsible for maintaining the cellular architecture, tracks for intracellular transport, positioning of organelles, assembly of cilia and flagella. They mediate the bipolar spindle assembly for chromosomal segregation and positioning of the cell division plate in dividing cells. The formation of microtubule complex structures depends on the cell type, cell stage, and cell function.
02:17Microtubule Instability
Microtubules are hollow cylindrical filaments having a diameter of approximately 25 nm and a length that varies from 200 nm to 25 μm. GTP-bound tubulin subunits form αβ-heterodimers for microtubule assembly. These core building blocks interact longitudinally, polymerizing into protofilaments. The protofilaments then interact with one another through lateral bonding forces to form stable cylindrical microtubules. These cylindrical filaments are dynamic as they undergo repeated assembly and...