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Myosin V exhibits a high duty cycle and large unitary displacement.

ABSTRACT: Myosin V is a double-headed unconventional myosin that has been implicated in organelle transport. To perform this role, myosin V may have a high duty cycle. To test this hypothesis and understand the properties of this molecule at the molecular level, we used the laser trap and in vitro motility assay to characterize the mechanics of heavy meromyosin-like fragments of myosin V (M5(HMM)) expressed in the Baculovirus system. The relationship between actin filament velocity and the number of interacting M5(HMM) molecules indicates a duty cycle of > or =50%. This high duty cycle would allow actin filament translocation and thus organelle transport by a few M5(HMM) molecules. Single molecule displacement data showed predominantly single step events of 20 nm and an occasional second step to 37 nm. The 20-nm unitary step represents the myosin V working stroke and is independent of the mode of M5(HMM) attachment to the motility surface or light chain content. The large M5(HMM) working stroke is consistent with the myosin V neck acting as a mechanical lever. The second step is characterized by an increased displacement variance, suggesting a model for how the two heads of myosin V function in processive motion.

SUBMITTER: Moore JR

PROVIDER: S-EPMC2198872 | biostudies-literature | 2001 Nov

REPOSITORIES: biostudies-literature

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Myosin V exhibits a high duty cycle and large unitary displacement.

Moore J R JR Krementsova E B EB Trybus K M KM Warshaw D M DM

The Journal of cell biology 20011112 4

Myosin V is a double-headed unconventional myosin that has been implicated in organelle transport. To perform this role, myosin V may have a high duty cycle. To test this hypothesis and understand the properties of this molecule at the molecular level, we used the laser trap and in vitro motility assay to characterize the mechanics of heavy meromyosin-like fragments of myosin V (M5(HMM)) expressed in the Baculovirus system. The relationship between actin filament velocity and the number of inter ...[more]

PMID: 11706052

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Project description:BackgroundMolecular techniques are increasingly employed to recognize the presence of cryptic species, even among commonly observed taxa. Previous studies have demonstrated that bats using high-duty cycle echolocation may be more likely to speciate quickly. Pteronotus parnellii is a widespread Neotropical bat and the only New World species to use high-duty cycle echolocation, a trait otherwise restricted to Old World taxa. Here we analyze morphological and acoustic variation and genetic divergence at the mitochondrial COI gene, the 7th intron region of the y-linked Dby gene and the nuclear recombination-activating gene 2, and provide extensive evidence that P. parnellii is actually a cryptic species complex.ResultsCentral American populations form a single species while three additional species exist in northern South America: one in Venezuela, Trinidad and western Guyana and two occupying sympatric ranges in Guyana and Suriname. Reproductive isolation appears nearly complete (only one potential hybrid individual found). The complex likely arose within the last ~6 million years with all taxa diverging quickly within the last ~1-2 million years, following a pattern consistent with the geological history of Central and northern South America. Significant variation in cranial measures and forearm length exists between three of the four groups, although no individual morphological character can discriminate these in the field. Acoustic analysis reveals small differences (5-10 kHz) in echolocation calls between allopatric cryptic taxa that are unlikely to provide access to different prey resources but are consistent with divergence by drift in allopatric species or through selection for social recognition.ConclusionsThis unique approach, considering morphological, acoustic and multi-locus genetic information inherited maternally, paternally and bi-parentally, provides strong support to conclusions about the cessation of gene flow and degree of reproductive isolation of these cryptic species.

Dataset Information

Myosin V exhibits a high duty cycle and large unitary displacement.

Publications

Myosin V exhibits a high duty cycle and large unitary displacement.

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