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Myosins are motor proteins in cells. They move along actin by changing shape after making stereospecific interactions with the actin subunits. As these are arranged helically, a succession of steps will follow a helical path. However, if the myosin heads are long enough to span the actin helical repeat (approximately 36 nm), linear motion is possible.(More)
Unlike wild-type mouse melanocytes, where melanosomes are concentrated in dendrites and dendritic tips, melanosomes in dilute (myosin Va-) melanocytes are concentrated in the cell center. Here we sought to define the role that myosin Va plays in melanosome transport and distribution. Actin filaments that comprise a cortical shell running the length of the(More)
Mouse myosin V is a two-headed unconventional myosin with an extended neck that binds six calmodulins. Double-headed (heavy meromyosin-like) and single-headed (subfragment 1-like) fragments of mouse myosin V were expressed in Sf9 cells, and intact myosin V was purified from mouse brain. The actin-activated MgATPase of the tissue-purified myosin V, and its(More)
Acanthamoeba myosins IA and IB were found to have molecular weights of 159,000 and 150,000 and Stokes radii of 6.2 and 5.9 nm, respectively. Both enzymes have frictional ratios of 1.7. Myosin IA consists of 22% alpha-helix, 32% beta-structure, and 46% unordered structure, while myosin IB is 16% alpha-helix, 46% beta-structure, and 38% unordered. Both(More)
Dictyostelium cells that lack the myoB isoform were previously shown to exhibit reduced efficiencies of phagocytosis and chemotactic aggregation ("streaming") and to crawl at about half the speed of wild-type cells. Of the four other Dictyostelium myosin I isoforms identified to date, myoC and myoD are the most similar to myoB in terms of tail domain(More)
We have completely sequenced a gene encoding the heavy chain of myosin II, a nonmuscle myosin from the soil ameba Acanthamoeba castellanii. The gene spans 6 kb, is split by three small introns, and encodes a 1,509-residue heavy chain polypeptide. The positions of the three introns are largely conserved relative to characterized vertebrate and invertebrate(More)
The contractile vacuole (CV) complex in Dictyostelium is a tubulovesicular osmoregulatory organelle that exhibits extensive motility along the actin-rich cortex, providing a useful model for investigating myosin-dependent membrane transport. Here, we show that the type V myosin myoJ localizes to CV membranes and is required for efficient osmoregulation, the(More)
Little is known about how molecular motors bind to their vesicular cargo. Here we show that myosin-Va, an actin-based vesicle motor, binds to one of its cargoes, the melanosome, by interacting with a receptor-protein complex containing Rab27a and melanophilin, a postulated Rab27a effector. Rab27a binds to the melanosome first and then recruits melanophilin,(More)
Actin retrograde flow and actomyosin II contraction have both been implicated in the inward movement of T cell receptor (TCR) microclusters and immunological synapse formation, but no study has integrated and quantified their relative contributions. Using Jurkat T cells expressing fluorescent myosin IIA heavy chain and F-tractin-a novel reporter for(More)
Mutations of genes needed for melanocyte function can result in oculocutaneous albinism. Examination of similarities in human gene expression patterns by using microarray analysis reveals that RAB38, a small GTP binding protein, demonstrates a similar expression profile to melanocytic genes. Comparative genomic analysis localizes human RAB38 to the mouse(More)