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Results 1 - 6 of 6
EC Number
Crystallization
Reference
15N-HSQC spectrum of the 17.7 kDa R2 module of AlgE6, together with the assignments of the resonances. The backbone and the side-chain assignments are essentially complete, side-chain amide groups of all Asn and Gln are assigned. Most of the protons and the carbon atoms of aromatic side-chains are assigned
dynamic force spectroscopy and comparison of epimeases AlgE4, AlgE6, recombinant construct PKA1 composed of A- and R-modules from various AlgE's, as well as separate R- and A-modules. The strength of the protein-mannuronan interaction, at a loading rate of 0.6 nN/s, variy from 73 pN (AlgE4) to 144 pN (A-module). The potential width, that is, the distance from the activation barrier to the bound substrate molecule, is 0.23 nm for AlgE4, 0.19 nm for AlgE6 and 0.1 nm for the A-module. No attraction is observed between the R-module and the substrate. The observations indicate that the A-module contains the substrate binding site and that the R-module modulates the enzyme-substrate binding strength; dynamic force spectroscopy and comparison of epimerases AlgE4, AlgE6, recombinant construct PKA1 composed of A- and R-modules from various AlgE's, as well as separate R- and A-modules. The strength of the protein-mannuronan interaction, at a loading rate of 0.6 nN/s, vary from 73 pN (AlgE4) to 144 pN (A-module). The potential width, that is, the distance from the activation barrier to the bound substrate molecule, is 0.23 nm for AlgE4, 0.19 nm for AlgE6 and 0.1 nm for the A-module. No attraction is observed between the R-module and the substrate. The observations indicate that the A-module contains the substrate binding site and that the R-module modulates the enzyme-substrate binding strength
Dynamic Force Spectroscopy. The position of the activation barrier is 0.23 nm for the AlgE4 and 0.10 nm for its A-module. The lack of interaction observed between the R-module and mannuronan suggest that the A-module contains the binding site for the polymer substrate. The ratio between the epimerase-mannuronan dissociation rate and the catalytic rate for epimerization of single hexose residues suggests a processive mode of action of the AlgE4 epimerase yielding the observed sequence pattern in the uronan associated with the A-module of this enzyme
NMR structure of the R-module from AlgE4. The R-module folds into a right-handed parallel beta-roll. Its overall shape is an elongated molecule with a positively charged patch that interacts with the substrate. Titration of the R-module with thulium indicates possible calcium binding sites in the loops formed by the nonarepeat sequences in the N-terminal part of the molecule. Calcium binding is important for the stability of the R-module. Calcium ions can be incorporated in these loops without structural violations and changes
to 2.1 A resolution. Isoform AlgE4A folds into a right-handed parallel beta-helix structure. The alpha-helix is composed of four parallel beta-sheets, comprising 12 complete turns, and has an amphipathic alpha-helix near the N terminus. The catalytic site is positioned in a positively charged cleft formed by loops extending from the surface encompassing Asp152, an amino acid important for the reaction
to 2.1 A resolution. Isoform AlgG is a long right-handed parallel beta-helix with an elaborate lid structure. Residue His319 acts as the catalytic base and that Arg345 neutralizes the acidic group during the epimerase reaction. Water is the likely catalytic acid. Substrate docking studies suggest that a conserved electropositive groove facilitates polymannuronate binding and contains at least nine substrate binding subsite
Results 1 - 6 of 6