Structure and function of a novel coliphage-associated sialidase

A coliphage named 63D, isolated previously, associated sialidase as a compo nent of phage particles. In order to localize the enzyme in phage particles , phages were partially destroyed by sonication, and the disrupted particle s were size Fractionated using a sucrose density gradient. Sodium dodecyl s ulfate-polyacrylamide gel electrophoresis, enzyme assay and electron microg raphy of the fractions revealed the enzyme to be composed of four identical subunits with a molecular mass of 90 kDa, and the subunits were cross-link ed by disulfide bonds. Electron micrographic observation indicated that six enzyme molecules were localized in a phage tail plate as a hexagonal array . (C) 2000 Federation of European Microbiological Societies. Published by E lsevier Science B.V. All rights reserved.