Alcohol and Its Effects on the Binding of a Catalytically Significant Water Molecule in the Active Site of the Human α -Tubulin Acetyltransferase

Abstract

Human alpha-tubulin acetyltransferase 1 (h- α TAT1) is a GNAT-family enzyme responsible for acetylating lysine 40 of α -tubulin, a modification critical for microtubule stability and cellular functions such as intracellular transport and signaling. The enzyme’s catalytic activity relies on a well-ordered water molecule coordinated by conserved residues, including Q58, R158, and I64, which facilitate lysine deprotonation and acetyl transfer. Ethanol, a small amphiphilic molecule, is known to interact with proteins by forming hydrogen bonds and hydrophobic contacts, often disrupting structured water networks and altering enzyme dynamics. Although direct ethanol binding to h- α TAT1 has not been reported, previous studies suggest ethanol can inhibit protein function by displacing catalytic water and altering hydrogen bonding networks. Ethanol preferentially binds to hydrophobic residues like isoleucine, especially when located near polar amino acids such as glutamine, a configuration present in h- α TAT1’s active site. Chronic ethanol exposure has also been linked to disrupted microtubule acetylation, supporting a possible indirect effect on h- α TAT1 activity. These studies aim to elucidate the structural basis by which ethanol modulates acetyltransferase activity, with broader implications for understanding ethanol-induced cytoskeletal dysfunction. Our results suggest that EtOH has the potential to act as an antagonist and can disrupt the binding of acetyl-CoA to the active site of h- α TAT1. Future molecular dynamics simulations will investigate how ethanol may perturb the substrate-binding cleft of h- α TAT1 and other GNAT-family acetyltransferases such as MEC-17, both with and without acetyl-CoA.