Characterization of molecular mechanism of electrogenic transporters accompanying ion movement

点击翻译按钮获取中文摘要

To clarify the molecular mechanism of the electrogenic transporter accompanying ion movement, we precisely determined the transport of halorhodopsin, a light-driven Cl- pump (pHR) and human oligopeptide transporter (hPEPT1).(1) The crystal structure (PDB:3QBG) of pHR clearly shows that the amino acid residue, Ser 130 is located in the vicinity of the protonated Schiff base and forms the hydrogen bond to the Schiff vase. Based on the Cl- transport activities of mutant Ser130, it has turned out that Ser130 coordinates with PBS and functions as a molecular valve to hinder the internal leak, backflux of Cl- during anion-transport cycle.(2) We demonstrated that mutation of Ser302 located in the vicinity of His57 in PEPT1 caused the alkaline shift of the optimum pH in the transport activity. This shift demonstrates that the hydroxyl group of Ser302 forms the hydrogen-bonding with the imidazole of His57, which might keep the uptake activity optimum in the range of physiological intestinal pH.