title: Silent and functional changes in the periplasmic maltose-binding protein of Escherichia coli K12. I. Transport of maltose.
abstract: The malE gene encodes the periplasmic maltose-binding protein (MBP). Nineteen mutations that still permit synthesis of stable MBP were generated by random insertion of a BamHI octanucleotide into malE and six additional mutations by in-vitro recombinations between mutant genes. The sequence changes were determined; in most cases the linker insertion is accompanied by a small deletion (30 base-pairs on average). The mutant MBP were studied for export, growth on maltose and maltodextrins, maltose transport and binding, and maltose-induced fluorescence changes. Sixteen mutant MBP (out of 21 studied in detail) were found in the periplasmic space: 12 of them retained a high affinity for maltose, and 10 activity for growth on maltose. The results show that several regions of MBP are dispensable for stability, substrate binding and export. Three regions (residues 207 to 220, 297 to 303 and 364 to 370) may be involved in interactions with the MalF or MalG proteins. A region near the C-terminal end is important for maltose binding. Two regions of the mature protein (residues 18 to 42 and 280 to 296) are required for export to, or solubility in, the periplasm.
authors.affiliation: Unité de Programmation Moléculaire et Toxicologie Génétique, (CNRS UA271, INSERM U163), Institut Pasteur, Paris, France.
authors.forename: P
authors.initials: P
authors.lastname: Duplay
authors.forename: S
authors.initials: S
authors.lastname: Szmelcman
authors.forename: H
authors.initials: H
authors.lastname: Bedouelle
authors.forename: M
authors.initials: M
authors.lastname: Hofnung
mesh_terms: D018528:ATP-Binding Cassette Transporters; D000595:Amino Acid Sequence; D001483:Base Sequence; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005798:Genes, Bacterial; D008320:Maltose / Q000493:pharmacokinetics; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D033902:Periplasmic Binding Proteins
chemical_list: D018528:ATP-Binding Cassette Transporters; D002352:Carrier Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C461619:MalE protein, E coli; C079123:MalG protein, E coli; D058619:Maltose-Binding Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; C461599:maltose transport system, E coli; D008320:Maltose