Identification and characterization of functional subunits of Clostridium botulinum type A progenitor toxin involved in binding to intestinal microvilli and erythrocytes.

Clostridium botulinum type A hemagglutinin-positive progenitor toxin consists of three distinct components: neurotoxin (NTX), hemagglutinin (HA), and non-toxic non-HA (NTNH). The HA consists of four subcomponents designated HA1, 2, 3a and 3b. By employing purified toxin and GST-fusion proteins of each HA subcomponent, we found that the HA-positive progenitor toxin, GST-HA1 and GST-HA3b bind to human erythrocytes and microvilli of guinea pig upper small intestinal sections. The HA-positive progenitor toxin and GST-HA1 bind via galactose moieties, GST-HA3b binds via sialic acid moieties. GST-2 and GST-3a showed no detectable binding.