Mechanism of cGMP-gated channel block by intracellular polyamines |
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Authors: | Guo D Lu Z |
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Affiliation: | Department of Physiology, University of Pennsylvania, Philadelphia 19104, USA. |
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Abstract: | Polyamines block the retinal cyclic nucleotide-gated channel from both the intracellular and extracellular sides. The voltage-dependent mechanism by which intracellular polyamines inhibit the channel current is complex: as membrane voltage is increased in the presence of polyamines, current inhibition is not monotonic, but exhibits a pronounced damped undulation. To understand the blocking mechanism of intracellular polyamines, we systematically studied the endogenous polyamines as well as a series of derivatives. The complex channel-blocking behavior of polyamines can be accounted for by a minimal model whereby a given polyamine species (e.g., spermine) causes multiple blocked channel states. Each blocked state represents a channel occupied by a polyamine molecule with characteristic affinity and probability of traversing the pore, and exhibits a characteristic dependence on membrane voltage and cGMP concentration. |
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Keywords: | retinal cyclic guanine monophosphate–gated channel ion permeation protonation polyamine diamine |
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