E0036

Molecular Recognition of Alcohol: Structure and Molecular Dynamics of LUSH. Schoen W. Kruse^*, Rui Zhao^$, Dean P. Smith^#, and David N.M. Jones,^{* #}Dept. of Pharmacology, UT Southwestern, Dallas, Texas, USA, 75390, Depts. of ^*Pharmacology and ^$Biochemistry, Univ. of Colorado HSC, Denver, CO, USA, 80206.

There are 14 million alcoholics in the United States, making it the most widely used psychoactive drug in the country. Alcohols modulate the function and expression of ligand-gated ion channels (LGIC) such as γ-aminobutyric acid (GABA), N-methyl-D-aspartate (NMDA), and Glycine receptors. Ethanol depresses NMDA receptor activity while enhancing GABA_A and Glycine receptor activity at physiologically relevant concentrations, causing a decrease in neuronal activity. Alcohol specifically binds to these proteins, which is thought to induce a conformational change that alters receptor sensitivity. Characterization of these alcohol-binding sites may lead to the development of pharmacologically relevant therapies to treat alcohol dependence and toxicity. The details of the LGIC-alcohol interaction remain unclear because of the lack of structural information due to the difficulties in studying membrane-bound proteins by conventional structural approaches. Therefore, defining the nature of specific alcohol-binding sites must come from other model systems.

LUSH is a non-enzymatic alcohol-binding protein that displays in vivo binding specificity to ethanol, n-propanol, and n-butanol and is required for a normal sensory response to short n-alcohols in Drosophila melanogaster. We have recently solved the structures of LUSH in complex with the above-mentioned alcohols to 1.49Å, 1.45Å, and 1.25Å, respectively. Through analysis of these structures, we have been able to define the interactions involved in alcohol binding and specificity. Each alcohol is bound in the core of the protein and is stabilized by an intricate network of hydrogen bonds and van der Waals interactions. Molecular dynamic simulations suggest that the position of the ethanol is dependant on two hydrogen bonds. In comparison, only one hydrogen bond and interactions from the increased alkyl chain length determine the location of the butanol.

LUSH serves as an excellent system to study how alcohols affect protein function and structure and will be used to characterize the nature of specific alcohol-binding sites. The studies of LUSH will advance our understanding of the molecular actions of alcohols that are implicated in alcohol abuse and addiction. This may aid in the development of pharmacologically relevant drugs for the treatment of this disease.