title: Effect of cholesterol on the branched-chain amino acid transport system of Streptococcus cremoris.
abstract: The effect of cholesterol on the activity of the branched-chain amino acid transport system of Streptococcus cremoris was studied in membrane vesicles of S. cremoris fused with liposomes made of egg yolk phosphatidylcholine, soybean phosphatidylethanolamine, and various amounts of cholesterol. Cholesterol reduced both counterflow and proton motive force-driven leucine transport. Kinetic analysis of proton motive force-driven leucine uptake revealed that the Vmax decreased with an increasing cholesterol/phospholipid ratio while the Kt remained unchanged. The leucine transport activity decreased with the membrane fluidity, as determined by steady-state fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene incorporated into the fused membranes, suggesting that the membrane fluidity controls the activity of the branched-chain amino acid carrier.
authors.affiliation: Department of Microbiology, University of Groningen, Haren, The Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: Zheng
authors.forename: A J
authors.initials: AJ
authors.lastname: Driessen
authors.forename: W N
authors.initials: WN
authors.lastname: Konings
mesh_terms: D000597:Amino Acids, Branched-Chain / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002784:Cholesterol / Q000494:pharmacology*; D007700:Kinetics; D007930:Leucine / Q000378:metabolism*; D008081:Liposomes; D008560:Membrane Fluidity / Q000187:drug effects; D008561:Membrane Fusion; D008564:Membrane Potentials; D010713:Phosphatidylcholines / Q000378:metabolism; D010714:Phosphatidylethanolamines / Q000378:metabolism; D013291:Streptococcus / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D000597:Amino Acids, Branched-Chain; D008081:Liposomes; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D002784:Cholesterol; D007930:Leucine