Crystallization and preliminary X-ray analysis of the Streptomyces olivaceoviridis NgcE binding protein of the ABC transporter for N-acetylglucosamine

Abstract

The NgcE protein binds N-acetylglucosamine ( GlcNAc) as well as N,N'-diacetylchitobiose and is a component of the ABC transporter Ngc for GlcNAc uptake in Streptomyces olivaceoviridis. After cloning the corresponding gene in an Escherichia coli host, the NgcE protein was overproduced in a soluble form within the cytoplasm and purified to homogeneity by four consecutive chromatographic processes. Crystals of NgcE that grew in the presence of 1 mM GlcNAc, 20%(w/v) PEG MME 2000 and 100 mM Tris-HCl pH 8.5 had a plate-like shape and belonged to either space group P2(1)2(1)2 (unit-cell parameters a = 59.9, b= 153.0, c= 41.7 Angstrom) or P2(1)2(1)2(1) (a = 58.1, b= 96.3, c = 151.7 Angstrom). The former crystals diffracted to 1.8 Angstrom resolution and the latter to 2.2 Angstrom. Selenomethionine-containing crystals were generated under the same conditions and belonged to space group P2(1)2(1)2(1) with unit-cell parameters a = 58.4, b = 96.6, c = 152.5 Angstrom, and diffracted to 2.0 Angstrom resolution.