Construction of A-type botulinum toxin mutant and genetically engineered bacterium thereof

The invention relates to a meat toxin A mutant. The A-type carnotoxin mutant comprises a first peptide fragment and a second peptide fragment, wherein the first peptide fragment and the second peptide fragment are connected through an interchain disulfide bond; wherein compared with a light chain of the wild type A-type botulinum toxin, the first peptide fragment has mutation at the 134 < th > site and/or the 165 < th > site; and/or the second peptide fragment has at least one of the following mutation sites compared with a heavy chain of the wild type A-type botulinum toxin: the 791st site, the 967th site and the 1060th site. The A-type creotoxin mutant disclosed by the invention has the advantages of low mismatch rate of disulfide bonds, high biological activity and the like. 本发明涉及一种A型肉毒素突变体。A型肉毒素突变体包括：第一肽段和第二肽段，所述第一肽段和所述第二肽段通过链间二硫键相连；其中，所述第一肽段相较于野生型A型肉毒素的轻链，具有第134位和/或第165位的突变；和/或所述第二肽段相较于野生型A型肉毒素的重链，具有如下突变位点的至少之一：第791位、第967位和第1060位。本发明的A型肉毒素突变体具有二硫键的错配率低和生物活性高等优点。