Structural basis for sugar translocation through maltoporin channels at 3.1 A resolution.
Trimeric maltoporin (LamB protein) facilitates the diffusion of maltodextrins across the outer membrane of Gram-negative bacteria. The crystal structure of maltoporin from Escherichia coli, determined to a resolution of 3.1 angstroms, reveals an 18-stranded, antiparallel beta-barrel that forms the framework of the channel. Three inwardly folded loops contribute to a constriction about halfway through the channel. Six contingent aromatic residues line the channel and form a path from the vestibule to the periplasmic outlet. Soaking of a crystal with maltotriose revealed binding of the sugar to this hydrophobic track across the constriction, which suggests that maltose and linear oligosaccharides may be translocated across the membrane by guided diffusion along this path.
Schirmer
T
T
Department of Structural Biology, University of Basel, Switzerland.
Keller
T A
TA
Wang
Y F
YF
Rosenbusch
J P
JP
D001425:Bacterial Outer Membrane Proteins; D010582:Bacteriophage lambda / Q000378:metabolism; D001665:Binding Sites; D050260:Carbohydrate Metabolism; D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D003196:Computer Graphics; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000737:chemistry* / Q000378:metabolism; D006860:Hydrogen Bonding; D008320:Maltose / Q000378:metabolism*; D008958:Models, Molecular; D009844:Oligosaccharides / Q000378:metabolism*; D017354:Point Mutation; D011134:Polysaccharides / Q000378:metabolism; D018272:Porins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017510:Protein Folding; D017433:Protein Structure, Secondary; D011991:Receptors, Virus / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; D009844:Oligosaccharides; D011134:Polysaccharides; D018272:Porins; D011991:Receptors, Virus; C016532:maltoporins; D008320:Maltose; C008315:maltodextrin