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. 1988 Aug;54(2):233–239. doi: 10.1016/S0006-3495(88)82952-7

Structural aspects of the sarcoplasmic reticulum K+ channel revealed by gallamine block.

M A Gray 1, B Tomlins 1, R A Montgomery 1, A J Williams 1
PMCID: PMC1330289  PMID: 2462922

Abstract

We have studied single-channel conductance fluctuations of K+ channels present in the sarcoplasmic reticulum (SR) membrane systems of rabbit cardiac and skeletal muscle. K+ conductance through the channels is reversibly blocked by gallamine. Conductance block occurs only from the trans side of the channel and is resolved as a smooth reduction in the open state conductance. At a fixed K+ concentration, conduction decreases with increasing gallamine concentration and the data can be fitted to a single-site inhibition scheme. The degree of block seen at a constant gallamine concentration decreases as K+ concentration is increased, indicating competition between gallamine and K+. Gallamine block is voltage dependent, the degree of block increasing with increasing negative holding potential. Quantitative analysis of block yields a zero voltage dissociation constant of 55.3 +/- 16 microM and an effective valence of block of 0.93 +/- 0.12. We conclude that gallamine blocks by interacting with a site or sites located at an electrical distance 30-35% into the voltage drop from the trans side of the channel. This site must have a cross-sectional area of at least 1.2 nm2. The results of this study have been used to modify and extend our view of the structure of the channel's conduction pathway.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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