Cell surface myosin in cultured fibroblasts

Area of Science:

• Cell Biology
• Protein Biochemistry

Background:

• Fibroblast cell surface proteins play crucial roles in cellular functions.
• Identifying specific proteins like myosin on the cell membrane aids in understanding cell structure and behavior.

Purpose of the Study:

• To identify and characterize myosin as a surface component of L-929 mouse fibroblast cells.
• To determine if membrane-bound myosin is a glycoprotein.

Main Methods:

• Lactoperoxidase-catalyzed iodination (125I) to label surface proteins.
• Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to analyze protein molecular weight.
• Immunoprecipitation using fibroblast myosin antiserum.
• Analysis of glycoprotein markers using 14C-D-glucosamine and galactose oxidase/potassium borotritide treatment.

Main Results:

• Myosin, with a molecular weight of 200,000 daltons, was identified as a surface protein on L-929 fibroblasts.
• Labeled myosin was specifically precipitated by antimyosin antiserum from solubilized plasma membranes.
• A co-precipitating protein of 210,000 daltons was observed but did not directly bind antimyosin antibody.
• Membrane myosin did not incorporate 14C-D-glucosamine and was not labeled after galactose oxidase/potassium borotritide treatment.

Conclusions:

• Myosin is a component of the L-929 mouse fibroblast cell surface.
• Membrane-bound myosin is unlikely to be a glycoprotein.