Crystallization and Characterization of the l-Arabinose-binding Protein of Escherichia coli B/r

Abstract The l-arabinose-binding protein was purified by conventional methods from Escherichia coli cell paste and crystallized using 2-methyl-2,4-pentanediol. A molecular weight of 38,000 was determined using both ultracentrifugation and gel filtration. The amino acid composition revealed high concentrations of aspartic and glutamic residues and nonpolar amino acids. The presence of 2 cysteine residues was also demonstrated. The addition of l-arabinose did not produce changes in the circular dichroism spectra or sedimentation velocity coefficients, indicating that no gross structural alterations occur when the ligand is bound. Studies involving fluorescence spectroscopy and N-bromosuccinimide reactivity have shown that a change in the environment of some tryptophan residues occurs concomitantly with l-arabinose binding.