Crystallization and preliminary X-ray analysis of AlgS, a bacterial ATP-binding cassette (ABC) protein specific to macromolecule import

Sphingomonas sp. A1 possesses a macromolecule (alginate; average molecular size 25 700 Da) uptake system mediated by a novel pit-dependent ABC transpo rter. In this system, AlgS (363 amino-acid residues; 40 kDa) functions as a n ATPase and provides energy for the translocation of high molecular-weight alginate across the cytoplasmic membrane. Hexahistidine-tagged AlgS of Sph ingomonas sp. A1 was overexpressed in Escherichia coli and crystallized by means of the hanging-drop vapour-diffusion method with ammonium dihydrogen monophosphate as the precipitant. Preliminary X-ray analysis of the resulta nt crystals was performed; they belonged to the monoclinic space group P2(1 ) and had unit-cell parameters a = 57.4, b = 92.7, c = 65.8 Angstrom, beta = 102.3 degrees. X-ray diffraction data to 3.2 Angstrom have been collected from the native crystal.