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Nancy Adamek Michael A. Geeves Lynne M. Coluccio 《Cellular and molecular life sciences : CMLS》2011,68(1):139-150
Three heterozygous missense mutations in the motor domain of myosin 1c (Myo1c), which mediates adaptation in the inner ear,
are associated with bilateral sensorineural hearing loss in humans. With transient kinetic analyses, steady-state ATPase and
motility assays, and homology modeling, we studied the interaction of these mutants with nucleotide and actin using a truncated
construct, Myo1c1IQ-SAH, which includes an artificial lever arm. Results indicate that mutation R156W, near switch 1, affects the nucleotide-binding
pocket and the calcium binding by disrupting switch 1 movement. Mutation V252A, in the K helix of the upper 50 kDa domain,
showed reduced actin affinity consistent with disruption of communication between the actin- and nucleotide-binding sites.
T380M, in a Myo1c-specific insert in the HO linker, displayed aberrant changes in most kinetic parameters and uncoupling of
the ATPase from motility. These data allow for an interpretation of how these mutations might affect adaptation. 相似文献
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The motor protein myosin-I produces its working stroke in two steps 总被引:13,自引:0,他引:13
Many types of cellular motility, including muscle contraction, are driven by the cyclical interaction of the motor protein myosin with actin filaments, coupled to the breakdown of ATP. It is thought that myosin binds to actin and then produces force and movement as it 'tilts' or 'rocks' into one or more subsequent, stable conformations. Here we use an optical-tweezers transducer to measure the mechanical transitions made by a single myosin head while it is attached to actin. We find that two members of the myosin-I family, rat liver myosin-I of relative molecular mass 130,000 (M(r) 130K) and chick intestinal brush-border myosin-I, produce movement in two distinct steps. The initial movement (of roughly 6 nanometres) is produced within 10 milliseconds of actomyosin binding, and the second step (of roughly 5.5 nanometres) occurs after a variable time delay. The duration of the period following the second step is also variable and depends on the concentration of ATP. At the highest time resolution possible (about 1 millisecond), we cannot detect this second step when studying the single-headed subfragment-1 of fast skeletal muscle myosin II. The slower kinetics of myosin-I have allowed us to observe the separate mechanical states that contribute to its working stroke. 相似文献
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