EtOH and its metabolites interact in the EtOH binding site of BK channels that shares a structural similarity with the EtOH-metabolizing center of SDR-ADH.

The maxi-calcium-activated potassium channel (BK) is a prominent target of ethanol (EtOH) and its metabolites, acetaldehyde (ACA) and acetic acid (AA). To fully understand the effects of these molecules, it is important to study the combined effects of all three. GH3 cells were cultured under standard conditions. Patch-clamp recordings were performed in single-channel mode. To improve understanding of the putative EtOH-binding site at the BK channel, an in silico search for similar structures was carried out against the complete protein data bank (PDB) using TopDomain and TopMatch. Protein-ligand docking was performed using Autodock Vina (v1.2.3). AA at a concentration of 0.02% significantly increased the opening probability of BK channels when applied externally. However, in the presence of intracellular ACA, the effect of AA on channel activity was blocked in a dose-dependent manner. Structure analysis revealed that not only EtOH, AA, and ACA can interact with the channel in the same structural pocket, but also that several oxidoreductases such as SDR-ADH share a potential EtOH-binding domain with potassium (BK) and calcium (CASTOR) channels, which are among the structurally most similar PDB entries (z-score > 5.00). The nucleotide (NAD)-binding motif of SDR-ADH and the potassium channel GsuK have significant structural overlap with the putative EtOH-binding region of BK channels. Our structural data suggest a potential interference of NAD and EtOH binding in BK channels. The structural similarity also hints to a possible common enzymatic ancestor of SDR-ADH and the BK channel.