Steven K Doberstein

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Many of the proteins that are critical for Drosophila phototransduction assemble into a signaling complex, signalplex, through association with the PDZ-domain protein INAD. Some of these proteins depend on INAD for proper subcellular localization to the phototransducing organelle, the rhabdomere, making it difficult to assess any physiological function of(More)
We have reexamined the interaction of purified platelet profilin with actin and present evidence that simple sequestration of actin monomers in a 1:1 complex with profilin cannot explain many of the effects of profilin on actin assembly. Three different methods to assess binding of profilin to actin show that the complex with platelet actin has a(More)
Calmodulin is a highly conserved regulatory protein found in all eukaryotic organisms which mediates a variety of calcium ion-dependent signalling pathways. In the Drosophila retina, calmodulin was concentrated in the photoreceptor cell microvillar structure, the rhabdomere, and was found in lower amounts in the sub-rhabdomeral cytoplasm. This calmodulin(More)
Myosin-I is thought to supply the force for movement of cell membranes relative to actin filaments (reviewed in refs 1, 2), but confirmation of this hypothesis has been difficult because of the presence of multiple isoforms of myosin-I and other unconventional myosins in most cells. We report here the first evidence that a myosin-I isoform is essential for(More)
Acanthamoeba myosin-I bound to substrates of nitrocellulose or planar lipid membranes on glass moved actin filaments at an average velocity of 0.2 micron/s. This movement required ATP and phosphorylation of the myosin-I heavy chain. We prepared planar lipid membranes on a glass support by passive fusion of lipid vesicles (Brian, A. A., and H. M. McConnell.(More)
We used bacterially expressed beta-galactosidase fusion proteins to localize the phospholipid binding domain of Acanthamoeba myosin IC to the region between amino acids 701 and 888 in the NH2-terminal half of the tail. Using a novel immobilized ligand lipid binding assay, we determined that myosin I can bind to several different acidic phospholipids, and(More)
We determined the amino acid sequence of the actin monomer binding/actin filament severing protein actophorin from Acanthamoeba castellanii by automated Edman degradation of peptide fragments and by sequencing of full-length cDNA. Actophorin consists of 138 amino acids (calculated molecular weight of 15,543) and shares a high degree of sequence similarity(More)
We used fluorescence microscopy of live Acanthamoeba to follow the time course of the concentration of myosin-I next to the plasma membrane at sites of macropinocytosis and phagocytosis. We marked myosin-I with a fluorescently labeled monoclonal antibody (Cy3-M1.7) introduced into the cytoplasm by syringe loading. M1.7 binds myosin-IA and -IC without(More)
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