Macromolecules from Lobster Axon Membranes That Bind Cholinergic Ligands and Local Anesthetics

AUTOR(ES)

Denburg, Jeffrey L.

RESUMO

The technique of reversible equilibrium dialysis has been applied to the study of macromolecules that are essential for axonal conduction. A binding component from a preparation of an axon-plasma membrane has been characterized and shown to bind nicotine with a KD = 0.42 ± 0.04 μM and to the extent of 0.7 nmol/g of wet nerve. This binding was competitively blocked by acetylcholine (Ki = 43 ± 7 μM) and procaine (Ki = 2.9 ± 0.2 μM). This axonal macromolecule exhibits several of the properties of cholinergic postsynaptic receptors including its concentration in the tissue, blockade of its binding of nicotine by cholinergic drugs and α-bungarotoxin, and its phospholipoprotein nature. Some important differences are a lower affinity for acetylcholine and its binding of procaine. It is suggested that this nicotine receptor is on the internal surface of the axon plasma membrane and is a component common to both the Na+ and K+ gates.

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