生物大分子室级学术报告-Single molecule structural dynamics unravel the coexistence of futile and productive transport cycles of an ABC transporter
报告人：Dr. Oded Lewinson ，The Technion-Israel Institute of Technology ，The Ruth and Bruce Faculty of medicine
报告时间：2016年10月27日(周四） 上午10:00 - 11:30
From bacteria to man, ATP Binding Cassette (ABC) transporters comprise a very large super- family of proteins. These membrane embedded transporters actively pump a wide range of molecules through the permeability barriers of cell membranes. They are involved in most (if not all) physiological processes and are tightly linked to genetic human diseases such as CFTR. They are also directly responsible for tumor resistance to multiple chemotherapeutics, bacterial multidrug resistance (MDR), and bacterial virulence and pathogenesis. The past decade has seen a boom in structural studies of ABC transporters and this structural information provided an invaluable context for understanding the mechanism of action of ABC transporters. One mechanistic aspect of ABC transporters that remains poorly understood is the nature and dynamics of their conformational changes. Most of the knowledge that we have today regarding the conformations of ABC transporters stems from crystal structures that are static pictures of highly dynamic machines. ABC transporters are known to undergo dramatic conformational changes during their transport cycle and these movements are of course an essential and a fundamental part of the transport mechanism. Little we know of the extent of these movements and even less so of their dynamics. In this work we have addressed this “black box”.
Single molecule techniques have transformed the way we think of how proteins work. From a Michaelis-Menten perspective to the identification of sub-populations, memory landscapes, and other non Markovian behaviors of enzymes. Arguably one of the most powerful and informative techniques to study conformational changes and conformational dynamics at the single molecule level is single molecule FRET, combined with wide-field TIRF microscopy. We applied this approach to study the conformational cycle of the vitamin B12 transporter from BtuCD. Here, we present our recent findings, unraveling the existence of two parallel catalytic cycles. One cycle is productive while the other is futile, and an auxiliary protein shifts BtuCD between the two cycles by controlling its allosteric connectivity.