Subunit unbinding mechanics of dimeric wheat germ agglutinin (WGA) studied by atomic force microscopy

• Dimer unbinding mechanism of wheat germ agglutinin (WGA) was studied by force spectroscopy.
• Unbinding force increased at least twice as large after complex formation with glycophorin A.
• The dissociation rate of WGA dimer was estimated to be in the range of 0.01−0.02 /s.

Wheat germ agglutinin (WGA) is an oligomeric lectin widely used as a model of sugar moieties in biochemistry. Subunit association is important for the crosslinking function of WGA, so we used atomic force microscopy to measure the subunit unbinding force of dimeric WGA. We found that the average unbinding force of dimeric WGA is ∼55 pN at ∼1 nN/s loading rate, whereas this unbinding force is increased at least up to 100 pN when WGA is bound to glycophorin A. Moreover, the dissociation rate constant of WGA was calculated to be 1–2 × 10−2 s−1, suggesting that dimer dissociation is relatively fast.