Mutations in the A subunit affect yield, stability, and protease sensitivity of nontoxic derivatives of heat-labile enterotoxin.

摘要: Heat-labile toxin (LT) is a protein related to cholera toxin, produced by enterotoxigenic Escherichia coli strains, that organized as an AB5 complex. A number of nontoxic derivatives LT, useful for new or improved vaccines against diarrheal diseases mucosal adjuvants, have been constructed site-directed mutagenesis. Here we studied the biochemical properties mutants LT-K7 (Arg-7-->Lys), LT-D53 (Val-53-->Asp), LT-K63 (Ser-63-->Lys), LT-K97 (Val-97-->Lys), LT-K104 (Tyr-104-->Lys), LT-K114 (Ser-114-->Lys), and LT-K7/K97 (Arg-7-->Lys Val-97-->Lys). We found mutations in subunit may profound effects on ability form structure stability trypsin sensitivity purified proteins. Unstable mutants, during long-term storage at 4 degrees C, showed decrease amount assembled solution parallel appearance soluble monomeric B subunit. This finding suggests pentamer influenced which associated with it. Among seven tested, was be efficient production, extremely stable storage, resistant proteolytic attack, very immunogenic. In conclusion, good candidate development antidiarrheal adjuvants.