Effect of n-Alkanols on G-Protein α Subunits.

Guanine nucleotide binding (G)-proteins are GTP-driven allosteric proteins consisting of a single α subunit and a β and γ heterodimer. Gα subunits function as on/off switches based on the occupancy of the nucleotide-binding site, GTP or GDP, such that any alteration in nucleotide exchange modulates signal output. Our previous work has shown that haloalkanes and ethers inhibit GDP/GTP exchange on αi1, αi2 and αi3 subunits, but not the closely related αo. To test whether individual G-protein sensitivity correlates with n-alkanols potency and hydrophobicity, we studied the effects of n-alkanols of varied chain lengths on GDP/GTP exchange by Gαsubunits. n-alkanols (ethanol, butanol, pentanol, hexanol, heptanol, octanol and nonanol) showed differential effects on guanine nucleotide exchange by Gαi1, Gαi2 and Gαo. Based on our observations, we conclude that n-alkanols interact and modulate the activity of the G-α subunits to different extent, thereby uncoupling pathways known to modulate neuronal excitation.