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The alpha subunit of a voltage-sensitive sodium channel characteristic of denervated rat skeletal muscle was cloned and characterized. The cDNA encodes a 2018 amino acid protein (SkM2) that is homologous to other recently cloned sodium channels, including a tetrodotoxin (TTX)-sensitive sodium channel from rat skeletal muscle (SkM1). The SkM2 protein is no(More)
Sodium channels have four homologous domains (D1-D4) each with six putative transmembrane segments (S1-S6). The highly charged S4 segments in each domain are postulated voltage sensors for gating. We made 15 charge-neutralizing or -reversing substitutions in the first or third basic residues (arginine or lysine) by replacement with histidine, glutamine, or(More)
The effects of Brazilian scorpion Tityus serrulatus toxin gamma (TiTx gamma) were studied on voltage-gated Na+ channels from human heart (hHl) and rat skeletal muscle (rSkM1). The Na+ channels were expressed in Xenopus laevis oocytes, and Na+ currents were recorded using two-microelectrode voltage-clamp techniques. In control experiments, the threshold of(More)
Myosins and kinesins are molecular motors that hydrolyse ATP to track along actin filaments and microtubules, respectively. Although the kinesin family includes motors that move towards either the plus or minus ends of microtubules, all characterized myosin motors move towards the barbed (+) end of actin filaments. Crystal structures of myosin II (refs 3-6)(More)
Myosin VI is a reverse direction myosin motor that, as a dimer, moves processively on actin with an average center-of-mass movement of approximately 30 nm for each step. We labeled myosin VI with a single fluorophore on either its motor domain or on the distal of two calmodulins (CaMs) located on its putative lever arm. Using a technique called FIONA(More)
A pair of tyrosine residues, located on the cytoplasmic linker between the third and fourth domains of human heart sodium channels, plays a critical role in the kinetics and voltage dependence of inactivation. Substitution of these residues by glutamine (Y1494Y1495/QQ), but not phenylalanine, nearly eliminates the voltage dependence of the inactivation time(More)
Myosin VI is a reverse direction actin-based motor capable of taking large steps (30-36 nm) when dimerized. However, all dimeric myosin VI molecules so far examined have included non-native coiled-coil sequences, and reports on full-length myosin VI have failed to demonstrate the existence of dimers. Herein, we demonstrate that full-length myosin VI is(More)
Myosin VI moves toward the pointed (minus) end of actin filaments, the reverse direction of other myosin classes. The myosin VI structure demonstrates that a unique insert at the end of the motor repositions its lever arm and is at least in part responsible for the reversal of directionality. However, it has been proposed that there must be additional(More)
This study examines the steady state activity and in vitro motility of single-headed (S1) and double-headed (HMM) myosin VI constructs within the context of two putative modes of regulation. Phosphorylation of threonine 406 does not alter either the rate of actin filament sliding or the maximal actin-activated ATPase rate of S1 or HMM constructs. Thus, we(More)
Approximately one third of the Na+ channels expressed in denervated or developing skeletal muscle are tetrodotoxin (TTX) insensitive, with a Kd for channel blockade of approximately 1 microM, similar to that found for cardiac Na+ channels. We have recently reported the cloning of a putative Na+ channel subtype that is characteristic of denervated and(More)