Crystallization and preliminary X-ray analysis of the bacterial ATP-binding-cassette (ABC) protein MalK

The ATP-binding protein, MalK, of the bacterial ABC (ATP-binding-cassette) transport complex MalFGK2 provides the energy for the translocation of maltose and maltodextrins across the cytoplasmic membrane. The MalK protein from Salmonella typhimurium was overexpressed in Escherichia coli and crystallized by the hanging-drop method using (NH4)2SO4as a precipitant. The crystals belong to space group P6x22 (most probably x = 1 or 5) with cell dimensions a = 181.8 and c = 182.5 A, corresponding to three or four molecules per asymmetric unit. They diffract to a resolution of about 3 A on a synchrotron X-ray source and are suitable for structure determination.