Biophysics of gap junctions

摘要: Gap junction channels, now known to be formed of connexins, connect the interiors apposed cells. These channels can opened and closed by various physiological stimuli experimental treatments. They are permeable ions neutral molecules up a size about 1 kDa or 1.5 nm diameter, including second messengers metabolites. The processes gating permeation subject this review. Voltage is readily applied stimulus, transactional voltages, those between cytoplasm exterior, affect most junctions. Single channel transitions open states rapid presumably involve charge movement as occurs with electrically excitable nerve muscle. Identification domains charges domain replacement site-directed mutagenesis being pursued. Raising cytoplasmic H+ Ca2+ concentrations rapidly reduces junctional conductance, action generally reversible, at least in part. A number lipophilic alcohols, fatly acids volatile anesthetics have similar actions. Phosphorylation also modulates several cases, sites phosphorylation known. appear induced voltage. Permeability measurement indicates that aqueous diffusion only minor interactions wall. Differences among junctions known, but further characterization connexin cell specificity required.