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MPM-12: a monoclonal antibody that predominantly stains mitotic cells and recognizes a protein kinase
R K Ganju1, J E Penkala, D A Wright
1Department of Medical Oncology, University of Texas M. D. Anderson Cancer Center, Houston.
Abstract:
The monoclonal antibody MPM-12, raised by using partially purified extract of mitotic HeLa cells as the immunogen, preferentially stains the cytoplasm of mitotic cells by indirect immunofluorescence without exhibiting any species specificity. On immunoblots, MPM-12 recognizes three bands, of 155, 88, and 68 kDa, in mitotic HeLa cell extract but only the 68-kDa band in interphase cell extract. The 68-kDa band seems to be associated with chromatin while the other two are not. All three MPM-12 reactive peptides are phosphorylated, and the phosphorylation seems to be required for MPM-12 reactivity. The MPM-12 immunocomplexes exhibit autophosphorylating and histone H1 kinase activity.
Insights
Monoclonal antibody MPM-12 targets phosphorylated proteins in mitotic cells, identifying distinct molecular weight bands. This antibody reveals key differences between mitotic and interphase cell protein profiles.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Monoclonal antibodies are crucial tools for identifying specific cellular components.
- Understanding protein differences between cell cycle phases is vital for cell biology research.
Purpose of the Study:
- To characterize the monoclonal antibody MPM-12 and its reactivity with cellular proteins.
- To investigate the role of phosphorylation in MPM-12 antibody binding.
Main Methods:
- Indirect immunofluorescence staining of mitotic cells.
- Immunoblotting of mitotic and interphase HeLa cell extracts.
- Peptide analysis and kinase activity assays.
Main Results:
- MPM-12 preferentially stains mitotic cell cytoplasm and recognizes 155, 88, and 68 kDa proteins in mitotic cells.
- Only the 68 kDa protein, associated with chromatin, is detected in interphase cells.
- All recognized proteins are phosphorylated, and this phosphorylation is necessary for antibody reactivity.
- MPM-12 immunocomplexes display autophosphorylating and histone H1 kinase activity.
Conclusions:
- MPM-12 is a specific monoclonal antibody that recognizes phosphorylated proteins differentially expressed during mitosis.
- The antibody identifies distinct protein targets in mitotic versus interphase cells, highlighting cell cycle-specific modifications.
- MPM-12 may serve as a valuable probe for studying mitotic events and associated kinase activities.