title: Two-dimensional crystals of Escherichia coli maltoporin and their interaction with the maltose-binding protein.
abstract: We have reconstituted Escherichia coli maltoporin into phospholipid membranes at low lipid-to-protein ratios to produce two-dimensional crystals of this membrane protein. Electron microscopy of negatively stained membranes showed three different types of arrays, two of them hexagonal and the third rectangular, all diffracting to approximately (2 nm)-1. Furthermore, we have core-constituted maltoporin with the maltose-binding protein from E. coli, a soluble periplasmic protein that has been proposed to interact with maltoporin. One of the hexagonal arrays was found to bind maltose-binding protein molecules in a regular way, while the maltose-binding protein binding sites were not accessible in the other crystal forms. Difference maps from averaged decorated arrays and undecorated controls showed three symmetry-related maltose-binding protein binding sites per maltoporin trimer, of which not more than one is likely to be occupied at a given time. Using multivariate statistical analysis to select similar unit cells of the decorated maltoporin array, we have obtained a map showing the rough outline of a maltose-binding protein molecule interacting with the pore formed by a maltoporin trimer.
authors.affiliation: Department of Microbiology, University of Basel, Switzerland.
authors.forename: K A
authors.initials: KA
authors.lastname: Stauffer
authors.forename: A
authors.initials: A
authors.lastname: Hoenger
authors.forename: A
authors.initials: A
authors.lastname: Engel
mesh_terms: D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism / Q000648:ultrastructure*; D002352:Carrier Proteins / Q000378:metabolism / Q000648:ultrastructure*; D003461:Crystallography; D004926:Escherichia coli / Q000648:ultrastructure; D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; D058619:Maltose-Binding Proteins; D008563:Membrane Lipids / Q000737:chemistry; D008854:Microscopy, Electron; D009004:Monosaccharide Transport Proteins; D015999:Multivariate Analysis; D033902:Periplasmic Binding Proteins; D018272:Porins; D011487:Protein Conformation; D011991:Receptors, Virus / Q000378:metabolism / Q000648:ultrastructure*
chemical_list: D018528:ATP-Binding Cassette Transporters; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D046911:Macromolecular Substances; C461619:MalE protein, E coli; D058619:Maltose-Binding Proteins; D008563:Membrane Lipids; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D018272:Porins; D011991:Receptors, Virus; C016532:maltoporins; C461599:maltose transport system, E coli