Publication: How batrachotoxin modifies the sodium channel permeation pathway: computer modeling and site-directed mutagenesis
All || By Area || By Year| Title | How batrachotoxin modifies the sodium channel permeation pathway: computer modeling and site-directed mutagenesis | Authors/Editors* | Wang SY, Mitchell J, Tikhonov DB, Zhorov BS, Wang GK |
|---|---|
| Where published* | Molecular Pharmacology |
| How published* | Journal |
| Year* | 2006 |
| Volume | 69 |
| Number | 3 |
| Pages | 788-95 |
| Publisher | |
| Keywords | |
| Link | http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=16354762&query_hl=1&itool=pubmed_docsum |
| Abstract |
A structural model of the rNav1.4 Na+ channel with batrachotoxin (BTX) bound within the inner cavity suggested that the BTX pyrrole moiety is located between a lysine residue at the DEKA selectivity filter (Lys1237) and an adjacent phenylalanine residue (Phe1236). We tested this pyrrole-binding model by site-directed mutagenesis of Phe1236 at D3/P-loop with 11 amino acids. Mutants F1236D and F1236E expressed poorly, whereas nine other mutants either expressed robust Na+ currents, like the wild-type (F1236Y/Q/K), or somewhat reduced current (F1236G/A/C/N/W/R). Gating properties were altered modestly in most mutant channels, with F1236G displaying the greatest shift in activation and steady-state fast inactivation (-10.1 and -7.5 mV, respectively). Mutants F1236K and F1236R were severely resistant to BTX after 1000 repetitive pulses (+50 mV/20 ms at 2 Hz), whereas seven other mutants were sensitive but with reduced magnitudes compared with the wild type. It is noteworthy that rNav1.4-F1236K mutant Na+ channels remained highly sensitive to block by the local anesthetic bupivacaine, unlike several other BTX-resistant mutant channels. Our data thus support a model in which BTX, when bound within the inner cavity, interacts with the D3/P-loop directly. Such a direct interaction provides clues on how BTX alters the Na+ channel selectivity and conductance. |
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