Isolation of an abundant 50,000-dalton actin filament bundling protein from Dictyostelium amoebae.
A monomeric actin bundling protein with a native molecular weight of approximately 50,000 (ABP-50) has been isolated from amoebae of Dictyostelium discoideum. ABP-50 cross-links F-actin to form tightly packed bundles, some of which are highly ordered. It exhibits a Kd of 2.1 microM and a molar ratio to actin of 1:1 in bundles. Calcium and ATP at physiological concentrations have no effect on these activities. ABP-50 is immunologically unrelated to 30-kDa protein, a previously described bundling protein from Dictyostelium. Immunofluorescence with affinity-purified polyclonal antibodies indicates that ABP-50 is localized in regions of the amoeboid cell cortex containing actin bundles. The molar ratio of ABP-50 to actin is approximately 1:5 in vivo. Therefore, the abundance of ABP-50 suggests that it may be responsible for the majority of the bundling activity in these cells.
Demma
M
M
Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, New York 10461.
Warren
V
V
Hock
R
R
Dharmawardhane
S
S
Condeelis
J
J
D000199:Actins / Q000378:metabolism / Q000648:ultrastructure; D000906:Antibodies; D002458:Cell Fractionation; D002846:Chromatography, Affinity; D004023:Dictyostelium / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D008840:Microfilament Proteins / Q000302:isolation & purification* / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron; D008970:Molecular Weight
D000199:Actins; D000906:Antibodies; D008840:Microfilament Proteins; C052523:actin filament bundling proteins