2AGM : Solution structure of the R-module from AlgE4

  • Svein Valla (Contributor)
  • Reinhard Wimmer (Contributor)
  • Britt I. G. Svanem (Contributor)
  • Finn L. Aachmann (Norwegian University of Science and Technology) (Contributor)
  • Steffen Petersen (Contributor)
  • Peter G?ntert (Contributor)



Experimental Technique/Method:SOLUTION NMR
Release Date:2006-01-10
Deposition Date:2005-07-27
Revision Date:2008-04-30#2011-07-13
Molecular Weight:16976.01
Macromolecule Type:Protein
Residue Count:167
Atom Site Count:1194

In the bacterium Azotobacter vinelandii, a family of seven secreted and calcium-dependent mannuronan C-5 epimerases (AlgE1-7) has been identified. These epimerases are responsible for the epimerization of beta-d-mannuronic acid to alpha-l-guluronic acid in alginate polymers. The epimerases consist of two types of structural modules, designated A (one or two copies) and R (one to seven copies). The structure of the catalytically active A-module from the smallest epimerase AlgE4 (consisting of AR) has been solved recently. This paper describes the NMR structure of the R-module from AlgE4 and its titration with a substrate analogue and paramagnetic thulium ions. The R-module folds into a right-handed parallel beta-roll. The overall shape of the R-module is an elongated molecule with a positively charged patch that interacts with the substrate. Titration of the R-module with thulium indicated possible calcium binding sites in the loops formed by the nonarepeat sequences in the N-terminal part of the molecule and the importance of calcium binding for the stability of the R-module. Structure calculations showed that calcium ions can be incorporated in these loops without structural violations and changes. Based on the structure and the electrostatic surface potential of both the A- and R-module from AlgE4, a model for the appearance of the whole protein is proposed.
Date made available2006

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