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Removal of a Conserved Disulfide Bond Does Not Compromise Mechanical Stability of a VHH Antibody Complex
journal contribution
posted on 2019-07-01, 00:00 authored by Haipei Liu, Valentin Schittny, Michael A. NashSingle-domain VHH
antibodies are promising reagents for medical
therapy. A conserved disulfide bond within the VHH framework region
is known to be critical for thermal stability, however, no prior studies
have investigated its influence on the stability of VHH antibody–antigen
complexes under mechanical load. Here, we used single-molecule force
spectroscopy to test the influence of a VHH domain’s conserved
disulfide bond on the mechanical strength of the interaction with
its antigen mCherry. We found that although removal of the disulfide
bond through cysteine-to-alanine mutagenesis significantly lowered
VHH domain denaturation temperature, it had no significant impact
on the mechanical strength of the VHH:mCherry interaction with complex
rupture occurring at ∼60 pN at 103–104 pN/sec regardless of disulfide bond state. These results
demonstrate that mechanostable binding interactions can be built on
molecular scaffolds that may be thermodynamically compromised at equilibrium.