The modification of alpha-bungarotoxin by digestion with trypsin.
Two modified alpha-bungarotoxins (alpha-BuTX)2 were obtained by trypsin digestion. On mild tryptic digestion, alpha-BuTX could be cleaved at a single site to give the des-tetrapeptide alpha-BuTX, designated as des-(71-74)-alpha-BuTX. Further cleavage at Arg36-Gly37 yielded a double-chained product held together by five disulfides and designated double-chained des-(71-74)-alpha-BuTX. The des-(71-74)-alpha-BuTX had a similar CD spectrum and antigenicity to that of native alpha-BuTX, but had a lower toxicity and neuromuscular-blocking potency. This indicates that the C-terminal tail of alpha-BuTX had some effect on the toxin's biological activities. The double-chained des-(71-74)-alpha-BuTX also retained full antigenicity, but changed moderately in CD spectrum and decreased dramatically in toxicity and neuromuscular-blocking potency. These results suggested that the invariant region at Arg36-Gly37, previously thought to be essential for the neurotoxicity of alpha-BuTX due to its cationic group, might also play a critical role in maintaining the native conformation of the toxin.
D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002038:Bungarotoxins / Q000633:toxicity; D055598:Chemical Phenomena; D002621:Chemistry; D002942:Circular Dichroism; D005779:Immunodiffusion; D007928:Lethal Dose 50; D051379:Mice; D010446:Peptide Fragments / Q000633:toxicity; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D014357:Trypsin
D000596:Amino Acids; D002038:Bungarotoxins; D010446:Peptide Fragments; D014357:Trypsin