title: Crystal structures and solution conformations of a dominant-negative mutant of Escherichia coli maltose-binding protein.
abstract: A mutant of the periplasmic maltose-binding protein (MBP) with altered transport properties was studied. A change of residue 230 from tryptophan to arginine results in dominant-negative MBP: expression of this protein against a wild-type background causes inhibition of maltose transport. As part of an investigation of the mechanism of such inhibition, we have solved crystal structures of both unliganded and liganded mutant protein. In the closed, liganded conformation, the side-chain of R230 projects into a region of the surface of MBP that has been identified as important for transport while in the open form, the same side-chain takes on a different, and less ordered, conformation. The crystallographic work is supplemented with a small-angle X-ray scattering study that provides evidence that the solution conformation of unliganded mutant is similar to that of wild-type MBP. It is concluded that dominant-negative inhibition of maltose transport must result from the formation of a non-productive complex between liganded-bound mutant MBP and wild-type MalFGK2. A general kinetic framework for transport by either wild-type MalFGK2 or MBP-independent MalFGK2 is used to understand the effects of dominant-negative MBP molecules on both of these systems.
authors.affiliation: Department of Molecular Biology, Swedish Agricultural University, Uppsala, Sweden.
authors.forename: B H
authors.initials: BH
authors.lastname: Shilton
authors.forename: H A
authors.initials: HA
authors.lastname: Shuman
authors.forename: S L
authors.initials: SL
authors.lastname: Mowbray
mesh_terms: D018528:ATP-Binding Cassette Transporters; D001120:Arginine; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins; D008024:Ligands; D008320:Maltose / Q000378:metabolism; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D017354:Point Mutation; D011487:Protein Conformation; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D012996:Solutions; D014364:Tryptophan
chemical_list: D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; C461619:MalE protein, E coli; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D011993:Recombinant Fusion Proteins; D012996:Solutions; C461599:maltose transport system, E coli; D008320:Maltose; D014364:Tryptophan; D001120:Arginine