Huovinen T, Lindenburg L, Minter R, Hollfelder F. Multiplexed Affinity Characterization of Protein Binders Directly from a Crude Cell Lysate by Covalent Capture on Suspension Bead Arrays.
Anal Chem 2021;
93:2166-2173. [PMID:
33397084 PMCID:
PMC7861142 DOI:
10.1021/acs.analchem.0c03992]
[Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
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The precise determination of affinity and specificity is a crucial step in the
development of new protein reagents for therapy and diagnostics. Paradoxically, the
selection of protein binders, e.g., antibody fragments, from large combinatorial
repertoires is a rapid process compared to the subsequent characterization of selected
clones. Here we demonstrate the use of suspension bead arrays (SBA) in combination with
flow cytometry to facilitate the post-selection analysis of binder affinities. The array
is designed to capture the proteins of interest (POIs) covalently on the surface of
superparamagnetic color-coded microbeads directly from expression cell lysate, based on
SpyTag-SpyCatcher coupling by isopeptide bond formation. This concept was validated by
analyzing the affinities of a typical phage display output, i.e., clones consisting of
single-chain variable fragment antibodies (scFvs), as SpyCatcher fusions in 12- and
24-plex SBA formats using a standard three-laser flow cytometer. We demonstrate that the
equilibrium dissociation constants (Kd) obtained from
multiplexed SBA assays correlate well with experiments performed on a larger scale,
while the antigen consumption was reduced >100-fold compared to the conventional
96-well plate format. Protein screening and characterization by SBAs is a rapid and
reagent-saving analytical format for combinatorial protein engineering to address
specificity maturation and cross-reactivity profiling of antibodies.
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