muramidase and bromophenol-red

The binding sites in hen egg-white lysozyme for neutral bromophenol red (BPR) and ionized bromophenol blue (BPB) have been characterized at 2 A resolution. In either case, the dye-bound enzyme is active against the polysaccharide, but not against the cell wall. Both binding sites are outside, but close to, the hexasaccharide binding cleft in the enzyme. The binding site of BPR made up of Arg5, Lys33, Phe34, Asn37, Phe38, Ala122, Trp123 and possibly Arg125, is close to subsite F while that of BPB made up of Tyr20, Arg21, Asn93, Lys96, Lys97 and Ser100, is close to subsites A and B. The binding sites of the neutral dye and the ionized dye are thus spatially far apart. The peptide component of the bacterial cell wall probably interacts with these cells during enzyme action. Such interactions are perhaps necessary for appropriately positioning the enzyme molecule on the bacterial cell wall.

Topics: Binding Sites; Bromphenol Blue; Fourier Analysis; Indicators and Reagents; Macromolecular Substances; Models, Molecular; Muramidase; Phenolsulfonphthalein; X-Ray Diffraction

Bromophenol red (BPR) binds to lysozyme and inhibits its activity against bacterial cell walls, but not against the polysaccharide component of peptidoglycan. The binding site of BPR in the enzyme has been characterised by X-ray analysis of the complex at 5.5A resolution. The new binding site, which is outside the cleft close to subsite F, is presumably involved in interactions with the peptide component of peptidoglycan, in the action of lysozyme against bacterial cell walls.

Topics: Animals; Binding Sites; Chickens; Egg White; Micrococcus; Models, Molecular; Muramidase; Phenolsulfonphthalein; Protein Binding; Protein Conformation; Spectrophotometry; X-Ray Diffraction

Topics: Animals; Binding Sites; Chickens; Coloring Agents; Egg White; Micrococcus; Muramidase; Phenolphthaleins; Phenolsulfonphthalein; Thermodynamics