Crystal structure of AlgQ2, a macromolecule (alginate)-binding protein of Sphingomonas sp. A1 at 2.0A resolution.
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Momma K, Mikami B, Mishima Y, Hashimoto W, Murata K
Crystal structure of AlgQ2, a macromolecule (alginate)-binding protein of Sphingomonas sp. A1 at 2.0A resolution.
J Mol Biol. 2002 Mar 8;316(5):1051-9.
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- 11884143 [ View in PubMed]
- Abstract
Sphingomonas sp. A1 possesses a high molecular mass (average 25,700 Da) alginate uptake system mediated by a novel pit-dependent ABC transporter. The X-ray crystallographic structure of AlgQ2 (57,200 Da), an alginate-binding protein in the system, was determined by the multiple isomorphous replacement method and refined at 2.0 A resolution with a final R-factor of 18.3% for 15 to 2.0 A resolution data. The refined structure of AlgQ2 was comprised of 492 amino acid residues, 172 water molecules, and one calcium ion. AlgQ2 was composed of two globular domains with a deep cleft between them, which is expected to be the alginate-binding site. The overall structure is basically similar to that of maltose/maltodextrin-binding protein, except for the presence of an N2-subdomain. The entire calcium ion-binding site is similar to the site in the EF-hand motif, but comprises a ten residue loop. This calcium ion-binding site is about 40 A away from the alginate-binding site.