Binding mode of azide to ferric Aplysia limacina myoglobin. Crystallographic analysis at 1.9 Å resolution
✍ Scribed by Andrea Mattevi; Giuseppina Gatti; Alessandro Coda; Menico Rizzi; Paolo Ascenzi; Maurizio Brunori; Martino Bolognesi
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 620 KB
- Volume
- 4
- Category
- Article
- ISSN
- 0952-3499
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✦ Synopsis
The binding mode of azide to the ferric form of Aplysia limacina myoglobin has been studied by X-ray crystallography. The three-dimensional structure of the complex has been refined at 1.9 A resolution to a crystallographic R-factor of 13.9%, including 126 ordered solvent molecules. Azide binds to the heme iron, at the sixth co-ordination position, and is oriented towards the outer part of the distal site crevice. This orientation is stabilized by an ionic interaction with the side-chain of Arg66 (E10) which, from an outer orientation in the 'aquo-met' ligand-free myoglobin, folds back towards the distal site in the presence of the anionic ligand. In the absence of a hydrogen bond donor residue at the distal E7 position in Aplysia limacina myoglobin, a different polar residue, Arg66 at the E10 topological position, has been selected by molecular evolution in order to grant ligand stabilization.