Binding energy, conformational change, and the mechanism of transmembrane solute movements.

Phosphoenolpyruvate:carbohydrate phosphotransferase systems of bacteria.

“…It was proposed that the proton abstracted from the carbohydrate on its phosphorylation might be obligatorily released on the periplasmic side of the membrane as a consequence of the transport mechanism of the EII, thus explaining the inhibition of EII activity by the energized state of the membrane. If this were the case, the EII would be an electrogenic proton pump (434). Such a mechanism could also conserve more of the chemical energy of PEP, in the form of an electrochemical proton gradient, which would otherwise be "lost" in the mere transport and phosphorylation of a carbohydrate by the PTS (101).…”

Role of plasma membrane ligand-binding proteins in the hepatocellular uptake of albumin-bound organic anions

“…A class-specific ligand binding membrane protein, an antibody to which selectively inhibits hepatocellular uptake of the specific class of organic anions bound by the protein, could participate in carrier-mediated transport in several ways. The protein could serve as the actual transporter, itself carrying the ligand from one side of the plasma membrane to the other as it "flip-flops" or shuttles from the external to the internal surface of the membrane and back again, or undergoes an appropriate conformational change (106). In this setting, a single protein might represent the entire carrier machinery.…”

Difference between the E1 and E2 conformations of gastric H+/K+‐ATPase in a multilamellar lipid film system

“…Studies on soluble enzymes [18] suggest that such changes are essentially located in hinge regions between protein domains. However, no information is available yet about proteins involved in the transport of molecules or ions across a membrane.…”

“…Protection against trypsin of a 19‐kDa peptide in the membrane for the Na + /K + ‐ATPase [19] further suggests a protein major rearrangement with respect to the membrane. Scarborough [18] suggested that the ion‐binding and ATP‐hydrolysis sites were very close together and therefore that the E1‐E2 shift did not need a large movement in protein structure. Some authors assumed that conformational changes affected a small fraction of α helical segment [15].…”