Domain versatility in plant AB-toxins: evidence for a local, pH-dependent rearrangement in the 2gamma lectin site of the mistletoe lectin by applying ligand derivatives and modelling.

Mistletoe lectin is a potent biohazard. Lectin activity in the toxic dimer primarily originates from the 2gamma-subdomain (Tyr-site) of the B-subunit. Crystallographic information on lectin-sugar complexes is available only at acidic pH, where lectin activity is low. Thus, we mapped ligand-binding properties including comparison to ricin's Tyr-site at neutral pH. Using these results and molecular dynamics simulations, a local conformational change was rendered likely. The obtained structural information is valuable for the design of potent inhibitors.