Fast measurement of galactoside transport by lactose permease.
Lactose permease of Escherichia coli was reconstituted into vesicles of dimyristoylphosphatidylcholine, and the rate of galactoside counterflow was measured in the millisecond time range. The turnover number and the half-saturation constant for transport agree with the values known for cells. This result demonstrates that lactose permease is the sole protein necessary for galactoside transport. Furthermore, lactose permease seems not to require a high level of negatively charged lipids or a certain degree of unsaturation of the lipid hydrocarbon chains. However, the lipids must be in the fluid state, because the transport rate drastically decreases below the lipid ordered fluid phase transition.
Dornmair
K
K
Max-Planck-Institut für Biologie, Tübingen, Federal Republic of Germany.
Overath
P
P
Jähnig
F
F
D001693:Biological Transport, Active; D002462:Cell Membrane / Q000201:enzymology; D004134:Dimyristoylphosphatidylcholine / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D007700:Kinetics; D008081:Liposomes; D026901:Membrane Transport Proteins / Q000378:metabolism*; D009004:Monosaccharide Transport Proteins; D027981:Symporters; D013862:Thiogalactosides / Q000378:metabolism*; D013865:Thioglycosides / Q000378:metabolism*
D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D008081:Liposomes; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D027981:Symporters; D013862:Thiogalactosides; D013865:Thioglycosides; C031803:thiodigalactoside; C021499:lactose permease; D004134:Dimyristoylphosphatidylcholine