title: Undecided membrane proteins insert in random topologies. Up, down and sideways: it does not really matter.
abstract: It is usually assumed that to ensure proper function, membrane proteins must be inserted in a unique topology. However, a number of dimeric small multidrug transporters can function in the membrane in various topologies. Thus, the dimers can be a random mixture of NiCi (N and C termini facing the cell cytoplasm) and NoCo (N and C termini facing the outside) orientation. In addition, the dimer functions whether the two protomers are parallel (N and C termini of both protomers on the same side of the membrane) or antiparallel (N and C termini of each protomer on opposite sides of the membrane). This unique phenomenon provides strong support for a simple mechanism of transport where the directionality is determined solely by the driving force.
authors.affiliation: Department of Biological Chemistry, Alexander Silberman Institute of Life Sciences, Hebrew University of Jerusalem, 91904 Jerusalem, Israel. shimon.schuldiner@huji.ac.il
authors.forename: Shimon
authors.initials: S
authors.lastname: Schuldiner
mesh_terms: D017920:Antiporters / Q000737:chemistry* / Q000235:genetics; D002462:Cell Membrane / Q000737:chemistry; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D011487:Protein Conformation; D055503:Protein Multimerization; D021381:Protein Transport; D013329:Structure-Activity Relationship
chemical_list: D017920:Antiporters; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; C075436:EmrE protein, E coli