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Myosin-I in mammalian liver
1Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia 30322.
Cell Motility and the Cytoskeleton
|January 1, 1993
Summary
Researchers identified two novel myosin-I polypeptides in rat liver, crucial for cell motility. These proteins bind actin and calmodulin, suggesting multiple myosin-I forms exist in higher organisms and within single cell types.
Area of Science:
- Biochemistry
- Cell Biology
- Molecular Biology
Background:
- Myosin-I is a class of 110-kDa proteins involved in cellular motility processes like migration and phagocytosis.
- While found in various higher eukaryotic tissues, the specific forms and functions of myosin-I in mammalian liver were previously unclear.
Purpose of the Study:
- To purify and characterize myosin-I polypeptides from rat liver.
- To investigate the functional characteristics and relationships of these liver myosin-I forms.
Main Methods:
- Protein purification using ATP solubilization and gel filtration.
- Biochemical assays including calmodulin binding, F-actin binding, and ATPase activity measurements.
- Immunological characterization using polyclonal antisera and proteolysis studies.
Main Results:
- Two distinct rat liver polypeptides (110-kDa and 130-kDa) with myosin-I characteristics were purified.
- Both polypeptides bind F-actin and calmodulin, exhibit actin-activated Mg(2+)-ATPase activity, and crosslink actin filaments.
- Immunological data and proteolysis indicate the polypeptides are distinct but related, with specific antibodies recognizing each.
Conclusions:
- Multiple myosin-I molecules are present in higher organisms, potentially coexisting within a single cell type.
- The purified rat liver polypeptides represent novel forms of myosin-I with functional similarities to brush border myosin-I.