Affinity enhancement of a recombinant antibody: formation of complexes with multiple valency by a single-chain Fv fragment-core streptavidin fusion.
In antigen-antibody interactions, the high avidity of antibodies depends on the affinity and number of the individual binding sites. To develop artificial antibodies with multiple valency, we have fused the single-chain antibody Fv fragments to core streptavidin. The resulting fusion protein, termed scFv::strep, was found after expression in Escherichia coli in periplasmic inclusion bodies. After purification of the recombinant product by immobilized metal affinity chromatography, refolding and size-exclusion FPLC, tetrameric complexes resembling those of mature streptavidin were formed. The purified tetrameric scFv::strep complexes demonstrated both antigen- and biotin-binding activity, were stable over a wide range of pH and did not dissociate at high temperatures (up to 70 degrees C). Surface plasmon resonance measurements in a BIAlite system showed that the pure scFv::strep tetramers bound immobilized antigen very tightly and no dissociation was measurable. The association rate constant for scFv::strep tetramers was higher than those for scFv monomers and dimers. This was also reflected in the apparent constants, which was found to be 35 times higher for pure scFv::strep tetramers than monomeric single-chain antibodies. We could also show that most of biotin binding sites were accessible and not blocked by biotinylated E.coli proteins or free biotin from the medium. These sites should therefore facilitate the construction of bispecific multivalent antibodies by the addition of biotinylated ligands.
Kipriyanov
S M
SM
Recombinant Antibody Research Group, Heidelberg, Germany.
Little
M
M
Kropshofer
H
H
Breitling
F
F
Gotter
S
S
Dübel
S
S
D000906:Antibodies / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000941:Antigens / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics* / Q000276:immunology; D001665:Binding Sites / Q000235:genetics; D001710:Biotin / Q000378:metabolism; D015153:Blotting, Western; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression / Q000235:genetics; D019791:Guanidine; D006146:Guanidines / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007128:Immunoglobulin Fragments / Q000235:genetics / Q000276:immunology*; D007135:Immunoglobulin Variable Region / Q000235:genetics / Q000276:immunology*; D007700:Kinetics; D010957:Plasmids / Q000235:genetics; D011485:Protein Binding; D011487:Protein Conformation; D011489:Protein Denaturation; D017510:Protein Folding; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D019809:Streptavidin; D013696:Temperature
D000906:Antibodies; D000941:Antigens; D001426:Bacterial Proteins; D006146:Guanidines; D007128:Immunoglobulin Fragments; D007135:Immunoglobulin Variable Region; D011993:Recombinant Fusion Proteins; D001710:Biotin; D019809:Streptavidin; D019791:Guanidine