title: Strategy for purifying maltose binding protein fusion proteins by affinity precipitation.
abstract: The maltose binding protein (MBP) affinity tag has been extensively used for protein purification. A commercial grade cationic starch could precipitate MBP or an MBP-tagged protein quantitatively by simultaneous addition of 10% (w/v) polyethylene glycol (PEG) and 50 mM calcium chloride. The precipitated MBP or MBP-tagged protein could be selectively dissociated by suspending the precipitate in 1 M NaCl. In the case of a soluble MBP fusion with a fragment of human immunodeficiency virus protein gp120, 38% of the contaminating proteins could be removed by precipitation with PEG/CaCl(2) and 100% of the fusion protein was recovered. In all cases, the purified proteins showed a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the expected changes in fluorescence emission spectra upon binding to maltose.
authors.affiliation: Chemistry Department, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
authors.forename: Smita
authors.initials: S
authors.lastname: Raghava
authors.forename: Samina
authors.initials: S
authors.lastname: Aquil
authors.forename: Sanchari
authors.initials: S
authors.lastname: Bhattacharyya
authors.forename: Raghavan
authors.initials: R
authors.lastname: Varadarajan
authors.forename: Munishwar N
authors.initials: MN
authors.lastname: Gupta
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry*; D011232:Chemical Precipitation; D002846:Chromatography, Affinity / Q000379:methods*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D058619:Maltose-Binding Proteins; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D002352:Carrier Proteins; D058619:Maltose-Binding Proteins; D011993:Recombinant Fusion Proteins