Crystallographic studies of archaeal light-driven ion pumps, including bacteriorhodopsin (BR) and halorhodopsin (HR), have shown that water molecules entrapped in protein cavities play an active role in the ion-translocation mechanism. On the basis of structural data of the reaction intermediates, we have proposed the hypothesis that BR functions as a proton/water antiporter, while HR functions as a proton/HCl antiporter.
The cystic fibrosis transmembrane conductance regulator (CFTR), a member of the ATP-binding cassette (ABC) transporter superfamily, is an anion channel which plays an important fundamental role in fluid and electrolyte transport across epithelial tissues. In the most of ABC transporters, two highly-conserved nucleotide-binding domains (NBDs) form a common engine that utilizes the energy of ATP hydrolysis to active-transport a wide spectrum of substrates. In CFTR, the ATP-dependent “NBD engine” drives the gate of the ion conducting pore by cycles of ATP binding and hydrolysis. In this review, we introduce the recent advances in the studies for the molecular mechanism of ATP-dependent NBD engine in CFTR channels.
The recently developed coarse-grained (CG) molecular model enables us to investigate meso-scopic morphologies of self-assembly of amphiphilic molecules at the molecular level. The present CG model is designed to well reproduce the interfacial properties, solvation free energy, as well as molecular distribution obtained from simulations at the all-atomic detail. The transferability and versatility is demonstrated by applying the model to the bulk aqueous solution as well as to the air/water interfacial system.