Dynamics, Conformational Transition and Drug Interactions of P-glycoprotein upon ATP Binding

• Main Authors: Hui-Hsuan Tu, 杜惠瑄
• Other Authors: Jung-Hsin Lin
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/54017745421265291780

碩士 === 國立臺灣大學 === 藥學研究所 === 93 === The overexpression of P-glycoprotein (Pgp) is one of the major causes of multidrug resistance (MDR) in cancer chemotherapies. Until now, it remains very challenging to obtain the high resolution Pgp structure and currently only low resolution electron microscopy structure is available. The recent determination of the X-ray crystallographic structure of a batcterial lipid A transporter, MsbA, has provided good structure templates for homology modeling of P-gp, and in our lab this model is used to further construct a full-length Pgp structure. We have conducted molecular dynamics (MD) simulation of the full-length Pgp in an excessively hydrated POPC bilayer. The starting structure was from a homology model but the N-terminal, C-terminal and the linker region were missing and therefore we have mended their structure. This mended structure was then energy minimized. The full-length Pgp was embed in the POPC bilayer and water was then added along the membrane normal direction to fully soak the whole system. The whole system was simulated in an environment closer to physiological condition with the salt concentration of 0.15M. Both free and ATP-bound Pgp forms of Pgp were simulated. The total simulation time was 9 ns for both simulations. On the other hand, we have conducted the docking simulation to find out the major transmembrane helices for drug binding. MD simulation provides very detailed structural information at atomic resolution. It was shown from our simulations that the overall architecture of the P-glycoprotein is stable in a realistic lipid bilayer environment, and the simulation results have allowed us to investigate the conformational changes of Pgp upon ATP binding in the efflux process. Not only the binding of ATP indeed drives the conformational changes in the TMDs, but also the helix rearrangements reduce the space of TMD center pore to mediate drug transportation. The mechanistic detail of the transport cycle upon binding ATP will be helpful to interpret remote connection between the binding of ATP and the subsequent release of substrates. The refined structure models of Pgp by our MD simulations may be used as the basis for designing Pgp inhibitors or “Pgp-ignoring drugs”.