Crystallization and preliminary X-ray analysis of alginate importer from Sphingomonas sp. A1

Sphingomonas sp. A1 directly incorporates alginate polysaccharides through a `superchannel' comprising a pit on the cell surface, alginate-binding proteins in the periplasm and an ABC transporter (alginate importer) in the inner membrane. Alginate importer, consisting of four subunits, AlgM1, AlgM2 and two molecules of AlgS, was crystallized in the presence of the binding protein AlgQ2. Preliminary X-ray analysis showed that the crystal diffracted to 3.3 Å resolution and belonged to space group P2₁2₁2₁, with unit-cell parameters a = 72.5, b = 136.8, c = 273.3 Å, suggesting the presence of one complex in the asymmetric unit.