Construction of antibody mimics from a noncatalytic enzyme-detection of polysialic acid

: Jokilammi A, Ollikka P, Korja M, Jakobsson E, Loimaranta V, Haataja S, Hirvonen H, Finne J

: 2004

: Journal of Immunological Methods

: Journal of immunological methods

: J Immunol Methods

: 295

: 1-2

: 149

: 60

: 12

: 0022-1759

DOI: https://doi.org/10.1016/j.jim.2004.10.006

We have used a conceptually novel way to construct antibody mimics based on the binding of a noncatalytic enzyme to its substrate. Bacteriophage-derived endosialidase cleaves polysialic acid (polySia), an important oncofetal and bacterial antigen, which is poorly immunogenic. We fused to green fluorescent protein (GFP) a catalytically inactive endosialidase known to bind but not degrade polysialic acid. The fusion protein is a convenient single-step reagent in fluorescence microscopy, binding assays and immunoblots. It efficiently and specifically detected polysialic acid in developing brain, neuroblastoma cells and bacteria causing meningitis. Enzyme-substrate interactions represent an unexploited source of molecular recognition events. Some of these could be used in designing well-defined substitute antibodies for the study of target molecules which are difficult to purify, available in low quantities, are unstable or have poor immunogenity.