title: Three-dimensional solution structure of the cytoplasmic B domain of the mannitol transporter IImannitol of the Escherichia coli phosphotransferase system.
abstract: The solution structure of the cytoplasmic B domain of the mannitol (Mtl) transporter (II(Mtl)) from the mannitol branch of the Escherichia coli phosphotransferase system has been solved by multidimensional NMR spectroscopy with extensive use of residual dipolar couplings. The ordered IIB(Mtl) domain (residues 375-471 of II(Mtl)) consists of a four-stranded parallel beta-sheet flanked by two helices (alpha(1) and alpha(3)) on one face and helix alpha(2) on the opposite face with a characteristic Rossmann fold comprising two right-handed beta(1)alpha(1)beta(2) and beta(3)alpha(2)beta(4) motifs. The active site loop is structurally very similar to that of the eukaryotic protein tyrosine phosphatases, with the active site cysteine (Cys-384) primed in the thiolate state (pK(a) < 5.6) for nucleophilic attack at the phosphorylated histidine (His-554) of the IIA(Mtl) domain through stabilization by hydrogen bonding interactions with neighboring backbone amide groups at positions i + 2/3/4 from Cys-384 and with the hydroxyl group of Ser-391 at position i + 7. Modeling of the phosphorylated state of IIB(Mtl) suggests that the phosphoryl group can be readily stabilized by hydrogen bonding interactions with backbone amides in the i + 2/4/5/6/7 positions as well as with the hydroxyl group of Ser390 at position i + 6. Despite the absence of any significant sequence identity, the structure of IIB(Mtl) is remarkably similar to the structures of bovine protein tyrosine phosphatase (which contains two long insertions relative to IIB(Mtl)) and the cytoplasmic B component of enzyme II(Chb), which fulfills an analogous role to IIB(Mtl) in the N,N'-diacetylchitobiose branch of the phosphotransferase system. All three proteins utilize a cysteine residue in the nucleophilic attack of a phosphoryl group covalently bound to another protein.
authors.affiliation: Laboratory of Chemical Physics, NIDDK, National Institutes of Health, USA.
authors.forename: Patricia M
authors.initials: PM
authors.lastname: Legler
authors.forename: Mengli
authors.initials: M
authors.lastname: Cai
authors.forename: Alan
authors.initials: A
authors.lastname: Peterkofsky
authors.forename: G Marius
authors.initials: GM
authors.lastname: Clore
mesh_terms: D020816:Amino Acid Motifs; D001665:Binding Sites; D003545:Cysteine / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D009004:Monosaccharide Transport Proteins; D010455:Peptides / Q000737:chemistry; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000737:chemistry*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012694:Serine / Q000737:chemistry
chemical_list: D029968:Escherichia coli Proteins; D009004:Monosaccharide Transport Proteins; D010455:Peptides; D012694:Serine; D010770:Phosphotransferases; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C022358:mannitol PTS permease, E coli; D003545:Cysteine