A calcium channel mutation causing hypokalemic periodic paralysis

The only calcium channel mutation reported to date Is
a deletion In the gene for the DHP-receptor a1-subunit
resulting In neonatal death in muscular dysgenesls
mice (1). In humans, this gene maps to chromosome
1q31-32. An autosomal dominant muscle disease,
hypokalemic periodic paralysis (HypoPP), has been
mapped to the same region (2). Sequencing of cDNA
of two patients revealed a G-to-A base exchange of
nucleotide 1583 predicting a substitution of histldlne
for arglnine528
. This affects the outermost positive
charge in the transmembrane segment IIS4 that Is
considered to participate in voltage sensing. By
restriction fragment analysis, the mutation was
detected in the affected members of 9 out of 25 HypoPP
families. The results indicate that the DHP-receptor
a1-subunit mutation causes HypoPP. An altered
excitation - contraction coupling may explain the
occurrence of muscle weakness.
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