Related Experiment Video
Updated: Jan 8, 2026
Visualizing the Morphological Characteristics of Neuromuscular Junction in Rat Medial Gastrocnemius Muscle
Published on: May 17, 2022
270K microtubule-associated protein cross-reacting with anti-MAP2 IgG in the crayfish peripheral nerve axon
Abstract:
MAPs (microtubule-associated proteins) were isolated from crayfish walking leg nerves. A major MAP was identified as a high molecular weight protein (270K). This protein co-migrated with mammalian MAP2, stimulated the polymerization of rat brain tubulin into microtubules, and was heat resistant. Rotary shadowing revealed that the 270K MAP is a long thin flexible structure. It formed cross-bridges of fine strands, linking microtubules with each other in vitro. These strands resemble the cross-bridges between microtubules observed in the crayfish axon permeabilized with saponin and quick-frozen, deep-etched. Antibodies against mammalian MAP2 cross-reacted with this crayfish MAP and stained the axoplasm of the walking leg nerves. Thus MAPs, especially the 270K MAP, appear to be a major component of the cross-linking strands between microtubules observed in the crayfish axon.
Insights
Microtubule-associated proteins (MAPs) were isolated from crayfish nerves. A major 270K MAP protein forms cross-bridges between microtubules, similar to those seen in axons.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Microtubule-associated proteins (MAPs) are crucial for microtubule stability and organization in neurons.
- The structural components responsible for cross-linking microtubules in axons are not fully understood.
- Crayfish walking leg nerves provide a model system for studying axonal transport and structure.
Purpose of the Study:
- To isolate and characterize microtubule-associated proteins (MAPs) from crayfish walking leg nerves.
- To identify the major MAP involved in cross-linking microtubules within the crayfish axon.
- To investigate the structural and functional properties of this major MAP.
Main Methods:
- Isolation of MAPs from crayfish walking leg nerve homogenates.
- Protein identification using co-migration with mammalian MAP2 and molecular weight analysis (270K).
- In vitro polymerization assays using rat brain tubulin.
- Structural analysis via rotary shadowing.
- Immunological cross-reactivity studies using antibodies against mammalian MAP2.
- Microscopy of permeabilized and quick-frozen crayfish axons.
Main Results:
- A major heat-resistant MAP of 270K molecular weight was isolated.
- This 270K MAP co-migrated with mammalian MAP2 and stimulated tubulin polymerization.
- Rotary shadowing revealed a long, thin, flexible structure for the 270K MAP.
- The 270K MAP formed in vitro cross-bridges linking microtubules, resembling structures observed in crayfish axons.
- Antibodies to mammalian MAP2 cross-reacted with the crayfish MAP and stained axoplasm.
Conclusions:
- Microtubule-associated proteins (MAPs), particularly the 270K MAP, are major components of the cross-linking structures between microtubules in crayfish axons.
- The identified 270K MAP shares characteristics with mammalian MAP2, suggesting conserved functions.
- These findings elucidate the molecular basis of microtubule organization within the crayfish axon.
