Steffen M. Sedlak, Leonard C. Schendel, Marcelo C. R. Melo, Diana A. Pippig,
Zaida Luthey-Schulten, Hermann E. Gaub, and Rafael C. Bernardi.
Direction matters: Monovalent streptavidin/biotin complex under load.
Nano Letters, 19:3415-3421, 2019.
(PMC: PMC6486461)
SEDL2019-RB
Novel site-specific attachment strategies combined with improvements of
computational resources enable new insights into the mechanics of the
monovalent biotin/streptavidin complex under load and forced us to rethink
the
diversity of rupture forces reported in the literature. We discovered that the
mechanical stability of this complex depends strongly on the geometry in
which
force is applied. By atomic force microscopy-based single molecule force
spectroscopy we found unbinding of biotin to occur beyond 400 pN at force
loading rates of 10 nN/s when monovalent streptavidin was tethered at its C-
terminus. This value is about twice as high than that for N-terminal
attachment.
Steered molecular dynamics simulations provided a detailed picture of the
mechanics of the unbinding process in the corresponding force loading
geometries. Using machine learning techniques, we connected findings from
hundreds of simulations to the experimental results, identifying different
force
propagation pathways. Interestingly, we observed that depending on force
loading geometry, partial unfolding of N-terminal region of monovalent
streptavidin occurs before biotin is released from the binding pocket.
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