Electron microscopic localization of myosin II and ABP-120 in the cortical actin matrix of Dictyostelium amoebae using IgG-gold conjugates.
To narrow the field of possible functions of an actin-binding protein (ABP-120) and myosin II, we have used high resolution immunocytochemistry with IgG-colloidal gold conjugates to identify the types of actin containing structures with which these proteins are associated in the isolated cell cortex. Staining for myosin II and ABP-120 is associated with distinct regions of the actin cytoskeleton in isolated cortices. Myosin II is localized to lateral arrays of filaments, where it is clustered and has a density that is unrelated to distance from the plasma membrane. Staining for myosin II is associated also with unidentified cytoplasmic vesicles. However, staining for ABP-120 is concentrated in dense networks of branched microfilaments that are adjacent to the plasma membrane or in surface projections (residual pseudopods and lamellopods). These results are consistent with a role for ABP-120 in the formation of filament networks in vivo and further suggest that networks of branched microfilaments are unlikely to participate in motility that is mediated by myosin II.
Ogihara
S
S
Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461.
Carboni
J
J
Condeelis
J
J
D000199:Actins / Q000032:analysis*; D002352:Carrier Proteins / Q000032:analysis*; D004023:Dictyostelium / Q000648:ultrastructure*; D006046:Gold; D007074:Immunoglobulin G; D007202:Indicators and Reagents; D008840:Microfilament Proteins / Q000032:analysis*; D008854:Microscopy, Electron / Q000379:methods; D009218:Myosins / Q000032:analysis*
D000199:Actins; D002352:Carrier Proteins; D007074:Immunoglobulin G; D007202:Indicators and Reagents; D008840:Microfilament Proteins; D006046:Gold; D009218:Myosins