title: Identical mutations at corresponding positions in two homologous proteins with nonidentical effects.
abstract: The x-ray structure of a mutant (Gly72 to Asp) of the Escherichia coli ribose-binding protein with altered transport function has been solved and refined to 2.2-A resolution with a conventional R-factor (R-factor = [formula: see text]) of 16.0% and good stereochemistry. Comparison with the wild type ribose-binding protein shows that the structure is disturbed little at the actual mutation site, but quite appreciably in a neighboring loop. Changes in the surface of the protein at the site of mutation, however, seem to explain the functional effects. A corresponding mutation of the related glucose/galactose-binding protein has different structural and functional effects due to the different structural context of the mutation site in that protein. These results are consistent with the concept that these proteins have slightly different ways of interacting with the membrane components in transport and chemotaxis.
authors.affiliation: Department of Molecular Biology, Swedish University of Agricultural Sciences, Uppsala.
authors.forename: A J
authors.initials: AJ
authors.lastname: Björkman
authors.forename: R A
authors.initials: RA
authors.lastname: Binnie
authors.forename: L B
authors.initials: LB
authors.lastname: Cole
authors.forename: H
authors.initials: H
authors.lastname: Zhang
authors.forename: M A
authors.initials: MA
authors.lastname: Hermodson
authors.forename: S L
authors.initials: SL
authors.lastname: Mowbray
mesh_terms: D000595:Amino Acid Sequence; D001224:Aspartic Acid; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002633:Chemotaxis; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005690:Galactose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005998:Glycine; D008958:Models, Molecular; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; D017354:Point Mutation; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D012266:Ribose / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D009004:Monosaccharide Transport Proteins; D033902:Periplasmic Binding Proteins; C028003:RbsB protein, E coli; C023550:galactose-binding protein; D001224:Aspartic Acid; D012266:Ribose; D005947:Glucose; D005998:Glycine; D005690:Galactose