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Determine the alkali metal cation selectivity and transport kinetics of purified, reconstituted voltage-dependent sodium channels isolated from rat skeletal muscle sarcolemma.

June 1, 1983Journal of Biological ChemistryOpen Access

Cation selectivity characteristics of the reconstituted voltage-dependent sodium channel purified from rat skeletal muscle sarcolemma.

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Determine the alkali metal cation selectivity and transport kinetics of purified, reconstituted voltage-dependent sodium channels isolated from rat skeletal muscle sarcolemma.
Purified sodium channel protein (980–2840 pmol saxitoxin binding/mg protein) was reconstituted into egg phosphatidylcholine vesicles and stimulated with either batrachotoxin (5 × 10⁻⁶ M) or veratridine (5 × 10⁻⁴ M).
Quenched-flow kinetic techniques were used to measure influx rates and equilibration half-times of ²²Na⁺, ⁴²K⁺, ⁸⁶Rb⁺, and ¹³⁷Cs⁺ at varying temperatures, alongside saxitoxin inhibition assays.
Batrachotoxin activation produced rapid influx with equilibration half-times at 18 °C of ≤50 ms for ²²Na⁺, 350 ms for ⁴²K⁺, 2.5 s for ⁸⁶Rb⁺, and 10 s for ¹³⁷Cs⁺, yielding a selectivity ratio of Na⁺ (1) : K⁺ (0.14) : Rb⁺ (0.02) : Cs⁺ (0.005) and saxitoxin block with Ki ≈ 5 × 10⁻⁹ M.
Veratridine activation caused much slower transport with equilibration half-times of 1.0, 1.2, 2.0, and 2.6 min at 36 °C for Na⁺, K⁺, Rb⁺, and Cs⁺, and exhibited higher activation energies (31 kcal/mol vs. 6.1–7.6 kcal/mol for batrachotoxin), showing channel opening is rate-limiting under veratridine.

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Implication

In vitro study reveals alkali cation selectivity in reconstituted rat skeletal muscle sodium channels, indicating distinct opening mechanisms between batrachotoxin and veratridine activation.

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Tanaka et al. (1983) studied this question.

synapsesocial.com/papers/6a762dff74b63c188eb222f9 https://doi.org/10.1016/s0021-9258(18)32208-7

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Implication

In vitro study reveals alkali cation selectivity in reconstituted rat skeletal muscle sodium channels, indicating distinct opening mechanisms between batrachotoxin and veratridine activation.

Cation selectivity characteristics of the reconstituted voltage-dependent sodium channel purified from rat skeletal muscle sarcolemma.

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Discussion

Implication

Cite This Study

Cation selectivity characteristics of the reconstituted voltage-dependent sodium channel purified from rat skeletal muscle sarcolemma.

Key Points

Discussion

Implication

Cite This Study

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