Construction of antibody mimics from a noncatalytic enzyme-detection of polysialic acid.
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.
Jokilammi
Anne
A
Department of Medical Biochemistry and Molecular Biology, University of Turku, Kiinamyllynkatu 10, FI-20520 Turku, Finland. anne.jokilammi@utu.fi
Ollikka
Pauli
P
Korja
Miikka
M
Jakobsson
Elina
E
Loimaranta
Vuokko
V
Haataja
Sauli
S
Hirvonen
Harri
H
Finne
Jukka
J
D000818:Animals; D000906:Antibodies / Q000276:immunology*; D019084:Fluorescent Antibody Technique, Indirect / Q000379:methods*; D049452:Green Fluorescent Proteins / Q000276:immunology / Q000378:metabolism; D006801:Humans; D008856:Microscopy, Fluorescence; D018716:Molecular Mimicry / Q000276:immunology*; D009439:Neuraminidase / Q000276:immunology / Q000378:metabolism*; D009447:Neuroblastoma / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000276:immunology / Q000378:metabolism; D012794:Sialic Acids / Q000276:immunology / Q000378:metabolism*
D000906:Antibodies; D011993:Recombinant Fusion Proteins; D012794:Sialic Acids; C021319:polysialic acid; D049452:Green Fluorescent Proteins; C035355:endo-N-acetylneuraminidase; D009439:Neuraminidase