Modulation of Na+ channel inactivation by the beta 1 subunit: a deletion analysis.
Na+ currents recorded from Xenopus oocytes expressing the Na+ channel alpha subunit alone inactivate with two exponential components. The slow component predominates in monomeric channels, while co-expression with the beta 1 subunit favors the fast component. Macropatch recordings show that the relative rates of these components are much greater than previously estimated from two-electrode measurements (approximately 30-fold vs approximately 5-fold). A re-assessment of steady-state inactivation, h infinity (V), shows that there is no depolarized shift of the slow component, provided a sufficiently long prepulse duration and repetition interval are used to achieve steady-state entry and recovery from inactivation, respectively. Deletion mutagenesis of the beta 1 subunit was used to define which regions of the subunit are required to modulate inactivation kinetics. The carboxy tail, comprising the entire predicted intracellular domain, can be deleted without a loss of activity; whereas small deletions in the extracellular amino domain or the signal peptide totally disrupt function.
Chen
C
C
Department of Neurology, Massachusetts General Hospital, Boston 02114, USA.
Cannon
S C
SC
D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004594:Electrophysiology; D007700:Kinetics; D008969:Molecular Sequence Data; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D012333:RNA, Messenger / Q000096:biosynthesis; D017384:Sequence Deletion; D015222:Sodium Channels / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*; D014982:Xenopus laevis
D012333:RNA, Messenger; D015222:Sodium Channels