Human sodium channel myotonia: slowed channel inactivation due to substitutions for a glycine within the III-IV linker.

1. Three families with a form of myotonia (muscle stiffness due to membrane hyperexcitability) clinically distinct from previously classified myotonias were examined. The severity of the disease greatly differed among the families. 2. Three dominant point mutations were discovered at the same nucleotide position of the SCN4A gene encoding the adult skeletal muscle Na+ channel alpha-subunit. The...

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Inactivation defects caused by myotonia-associated mutations in the sodium channel III-IV linker

Missense mutations in the skeletal muscle Na+ channel alpha subunit occur in several heritable forms of myotonia and periodic paralysis. Distinct phenotypes arise from mutations at two sites within the III-IV cytoplasmic loop: myotonia without weakness due to substitutions at glycine 1306, and myotonia plus weakness caused by a mutation at threonine 1313. Heterologous expression in HEK cells sh...

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Inactivation of the Sodium Channel

A B S X R A C T Gating current (I~) has been studied in relation to inactivation of the Na channels. No component of lg has the time course of inactivation; apparent ly little or no charge movement is associated with this step. Inactivation nonetheless affects Ig by immobilizing about two-thirds of gating charge. Immobilization can be followed by measuring ON charge movement dur ing a pulse and...

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Inactivation of the Sodium Channel

A B S X R A C T Gating current (I~) has been studied in relation to inactivation of the Na channels. No component of lg has the time course of inactivation; apparent ly little or no charge movement is associated with this step. Inactivation nonetheless affects Ig by immobilizing about two-thirds of gating charge. Immobilization can be followed by measuring ON charge movement dur ing a pulse and...

متن کامل

Inactivation of the Sodium Channel

A B S X R A C T Gating current (I~) has been studied in relation to inactivation of the Na channels. No component of lg has the time course of inactivation; apparent ly little or no charge movement is associated with this step. Inactivation nonetheless affects Ig by immobilizing about two-thirds of gating charge. Immobilization can be followed by measuring ON charge movement dur ing a pulse and...

متن کامل

Human sodium channel myotonia: slowed channel inactivation due to substitutions for a glycine within the III-IV linker.

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