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Localization of 350K molecular weight and related proteins in both the cytoskeleton and nuclear flecks that increase
Abstract:
Monoclonal and polyclonal antibodies were raised against the highest molecular weight microtubule-associated protein (MAP-1) isolated from brain. Immunoblotting with the antibodies revealed the presence of cross-reactive protein of 350K or less on whole cells, isolated nuclei and cellular microtubules. Two-dimensional peptide maps showed substantial homology of immunoprecipitated cellular proteins of 350K, 80K and 51K with a 25K fragment of brain MAP-1. On antibody staining, immunofluorescence was seen on a cytoplasmic network, the mitotic spindle, the centrosome, and intranuclear flecks. The antibody causing immunofluorescence in all these sites was absorbed most effectively with slices of blotted membrane which contained the 350K protein. These results suggest that the cross-reactive molecules in diverse sites belong to the family of the 350K protein. The number of nuclear flecks and the amount of bound radioactivity of 125I-antibody almost doubled during G1 phase.
Insights
Researchers developed antibodies against brain microtubule-associated protein 1 (MAP-1). These antibodies identified a 350K protein family in various cellular locations, including the nucleus, with increased nuclear presence during the G1 phase.
Area of Science:
- Cell Biology
- Neuroscience
- Molecular Biology
Background:
- Microtubule-associated proteins (MAPs) are crucial for microtubule stability and dynamics.
- Brain MAP-1 is a major MAP involved in neuronal structure and function.
Purpose of the Study:
- To generate and characterize antibodies against brain MAP-1.
- To investigate the presence and localization of MAP-1 related proteins in various cellular compartments.
Main Methods:
- Production of monoclonal and polyclonal antibodies against brain MAP-1.
- Immunoblotting and immunofluorescence microscopy for protein detection and localization.
- Two-dimensional peptide mapping for protein homology analysis.
Main Results:
- Antibodies recognized cross-reactive proteins of 350K or less in whole cells, nuclei, and microtubules.
- Homology was observed between immunoprecipitated cellular proteins and a MAP-1 fragment.
- Immunofluorescence revealed localization in the cytoplasm, mitotic spindle, centrosome, and intranuclear flecks.
- Nuclear flecks and antibody binding increased during the G1 phase.
Conclusions:
- The identified cross-reactive molecules belong to a 350K protein family.
- This protein family is present in diverse cellular locations, including the nucleus.
- Nuclear localization and binding of this protein family are cell cycle-dependent, particularly during G1 phase.