1. Currently I am working on a project on Inwardly-rectifying potassium channels (Kir). Kir channels play critical roles in the regulation of multiple cellular functions including membrane excitability, vascular tone, heart rate, renal salt flow, and insulin release. Previous studies from our lab have shown that the predominant effect of cholesterol on mammalian Kir channels is suppression of the channel function, an effect that was observed for most of the Kir. However, it is less known about the molecular mechanism responsible for the sensitivity of Kir channels to cholesterol. Our general hypothesis is that suppression of endothelial K+ channels plays a major role in endothelial dysfunction. The most fundamental question is to determine whether cholesterol binds directly to the Kir channelsâ€™ proteins and to identify the binding site. The goal of my current study is to address this question. The only direct and straightforward way to determine whether the effect of cholesterol on the channels is direct is to test whether cholesterol binds to the purified Kir channels and regulates their activity in a non-cellular environment. . However, no full length mammalian Kir channels have been purified. Therefore, to investigate cholesterol sensitivity of a bacterial analogue of Kir channels, KirBac1.1. These studies will help to determine whether cholesterol directly binds to KirBac1.1. and to elucidate molecular/structural basis for the sensitivity of KirBac1.1 channels to cholesterol.