Role of Myosin in Terminal Web Contraction in Isolated Intestinal Epithelial Brush Borders

• Published in: The Journal of cell biology 1985-05, Vol.100 (5), p.1647-1655
• Main Authors: Thomas C. S. Keller III, Conzelman, Karen A., Chasan, Rebecca, Mooseker, Mark S.
• Format: Article
• Language: English
• Subjects: Actins; Adenosine triphosphatases; Adenosine Triphosphate - physiology; Animals; Antibodies; Chickens; Cytoskeleton; Epithelial cells; Gels; Gizzard; Intestinal Mucosa - physiology; Intestinal Mucosa - ultrastructure; Microvilli; Microvilli - physiology; Myosins - immunology; Myosins - physiology; Phosphates; Phosphorylation; Protein Binding; Solubility
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.100.5.1647

We have investigated the role of myosin in contraction of the terminal web in brush borders isolated from intestinal epithelium. At 37°C under conditions that stimulate terminal web contraction (1 μM Ca++ and ATP), most (60-70%) of the myosin is released from the brush border. Approximately 80% of the myosin is also released by ATP at 0°C, in the absence of contraction. Preextraction of this 80% of the myosin from brush borders with ATP has no effect on either the time course or extent of subsequently stimulated contraction. However, contraction is inhibited by removal of all of the myosin with 0.6 M KCl and ATP. Contraction is also inhibited by an antibody to brush border myosin, which inhibits both the ATPase activity of brush border myosin and its ability to form stable bipolar polymers. These results indicate that although functional myosin is absolutely required for terminal web contraction only ∼20% of the brush border myosin is actually necessary. This raises the possibility that there are at least two different subsets of myosin in the terminal web.