Chen Zhao
PhD, Molecular Biophysics & Biochemistry, Yale University, New Haven, CT
BS, School of Life Sciences, University of Science and Technology of China
ATP-sensitive potassium channel (KATP) is an ion channel gated by ATP and ADP, and by doing so, it translates the metabolic state of a cell into electric signals. At molecular level, KATP is endowed with sensitivity to ATP and ADP through direct interactions with multiple binding sites. These binding sites are scattered across the entire KATP molecule, which is a tetramer of hetero-dimers that are composed of a type of inward rectifier potassium ion channel (Kir) and an ABC transporter (SUR). Previous studies have identified an inhibitory site on Kir that results in channel closure upon binding to ATP, and stimulatory sites on SUR that favor channel opening when occupied by either MgADP or MgATP. These observations pose a puzzle because in healthy cells ATP exists at millimolar concentrations whereas ADP is present only in the ten micromolar range. How then does KATP detect changes in ADP concentration when the background ATP concentration remains so high that ATP inhibition should dominate? To answer this question, we have to determine what the ATP and ADP affinities are at their respective sites and also understand how occupancy of these sites allosterically regulate the pore’s gate. Once this level of understanding is reached we can then try to predict the response of KATP to different metabolic states. Finally, we can integrate these responses into the broader signaling network that involves other closely related partners to describe the action of KATP at a systems biology level. My project in the MacKinnon lab aims to address this problem using a combination of electrophysiology and structural biology techniques.
