SUBCLONING AND CHARACTERIZATION OF THE BINDING DOMAIN OF FRAGMENT-B OF DIPHTHERIA-TOXIN

The binding domain (R domain) of diphtheria toxin as defined from the recently published crystal structure [Choe, Bennett, Fujii, Curmi, Kan tardjieff, Collier and Eisenberg (1992) Nature (London) 357, 216-222] was subcloned. The 17 kDa peptide containing amino acids 378-535 from fragment B of diphtheria toxin preceded by the tripeptide Met-His-Gly bound specifically and with high affinity to diphtheria-toxin receptor s. It efficiently inhibited the toxicity of full-length toxin. The bin ding domain entered the detergent phase of Triton X-114 at pH values b elow 6, indicating that it exposed hydrophobic regions at acidic pH.