The toxin abrin is a dimer consisting of two protein subunits, termed A and B. The B chain facilitates abrin's entry into a cell by bonding to certain transport proteins on cell membranes, which then transport the toxin into the cell. Once inside the cell, the A chain prevents protein synthesis by inactivating the 28S RNA of the ribosome. One molecule of abrin will inactivate up to 1,500 ribosomes per second. Symptoms are identical to those of ricin, except abrin is more toxic by almost two orders of magnitude; the fatal dose of abrin is approximately 1/75 that of the fatal dose of ricin (though the abrin in ingested seeds may be absorbed much more slowly than the ricin in Ricinus communis even if the seeds are chewed and the coat penetrated, allowing time for successful rescue efforts in at least some cases.) Abrin has an LD50 of only 0.56 μg/kg in mice, and Kingsbury lists a toxic dose in humans at 0.00015% body weight, or approximately 0.1 mg for a 68 kg (150 lb) human. Ingesting intact seeds may result in no clinical findings, as they can pass undigested through the gastrointestinal tract because of their hard shell. This plant is also poisonous to horses. Symptoms of poisoning include nausea, vomiting, convulsions, liver failure, and death, usually after several days.