4 research outputs found
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Cargo adaptors regulate stepping and force generation of mammalian dynein-dynactin.
Cytoplasmic dynein is an ATP-driven motor that transports intracellular cargos along microtubules. Dynein adopts an inactive conformation when not attached to a cargo, and motility is activated when dynein assembles with dynactin and a cargo adaptor. It was unclear how active dynein-dynactin complexes step along microtubules and transport cargos under tension. Using single-molecule imaging, we showed that dynein-dynactin advances by taking 8 to 32-nm steps toward the microtubule minus end with frequent sideways and backward steps. Multiple dyneins collectively bear a large amount of tension because the backward stepping rate of dynein is insensitive to load. Recruitment of two dyneins to dynactin increases the force generation and the likelihood of winning against kinesin in a tug-of-war but does not directly affect velocity. Instead, velocity is determined by cargo adaptors and tail-tail interactions between two closely packed dyneins. Our results show that cargo adaptors modulate dynein motility and force generation for a wide range of cellular functions
Recommended from our members
Cargo adaptors regulate stepping and force generation of mammalian dynein-dynactin.
Cytoplasmic dynein is an ATP-driven motor that transports intracellular cargos along microtubules. Dynein adopts an inactive conformation when not attached to a cargo, and motility is activated when dynein assembles with dynactin and a cargo adaptor. It was unclear how active dynein-dynactin complexes step along microtubules and transport cargos under tension. Using single-molecule imaging, we showed that dynein-dynactin advances by taking 8 to 32-nm steps toward the microtubule minus end with frequent sideways and backward steps. Multiple dyneins collectively bear a large amount of tension because the backward stepping rate of dynein is insensitive to load. Recruitment of two dyneins to dynactin increases the force generation and the likelihood of winning against kinesin in a tug-of-war but does not directly affect velocity. Instead, velocity is determined by cargo adaptors and tail-tail interactions between two closely packed dyneins. Our results show that cargo adaptors modulate dynein motility and force generation for a wide range of cellular functions
Rna Compaction in the Presence of Polyvalent Cations
The effects of polyvalent cations on the effective size and charge of double-stranded DNA (dsDNA) have been well studied. In the presence of polyvalent cations, dsDNA in dilute solution undergoes a single-molecule, first-order phase transition, otherwise called condensation: more explicitly, upon onset of 90% neutralization of the phosphate backbone, the DNA undergoes discontinuous compaction into tightly wound toroids. However, the effects of these cations on long single-stranded RNAs (ssRNA) have not been well characterized. In this study we use centrifugation methods to examine the effective size of long ssRNAs in solutions of increasing concentration of the tetravalent cation spermine. In contrast to the case of dsDNA, we find only a continuous decrease in the size of ssRNA upon increase in spermine concentration. However, the decrease is significant enough to suggest that RNA molecules longer than viral genomes can be packaged in vitro into virus-like vectors for gene delivery