N546 in beta18-beta19 loop is important for binding and toxicity of the Bacillus thuringiensis Cry1Ac toxin.
Our previous mutagenic analysis showed that the unique residue N546 in the apex of beta18-beta19 loop of Bacillus thuringiensis Cry1Ac toxin is important for its toxicity. In this study, trypsin digestion susceptibility, binding to BBMV and oligomer formation activity was therefore analyzed to determine the mechanism of toxicity change of these mutant toxins. The results showed that residue N546 was not involved in toxin oligomerisation and maintaining the stability of toxin, the enhanced toxicity of mutant N546A was just because of increased binding to BBMV, and reduction in toxicity of other mutants were caused by reduction in initial or irreversible binding to BBMV. This is the first report that revealed N546 in Cry1Ac domain III played an essential role in its insecticidal activity and binding to insect BBMV.
Xiang
Wang Fa
WF
Hunan Normal University, Changsha, China.
Qiu
Xia Li
XL
Zhi
Ding Xue
DX
Min
Zhao Xin
ZX
Yuan
Lv
L
Quan
Yu Zi
YZ
D000595:Amino Acid Sequence; D001413:Bacillus thuringiensis / Q000235:genetics* / Q000378:metabolism; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D001665:Binding Sites / Q000502:physiology; D018360:Crystallography, X-Ray; D004731:Endotoxins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D006460:Hemolysin Proteins / Q000737:chemistry* / Q000378:metabolism / Q000502:physiology; D008958:Models, Molecular; D009154:Mutation; D017434:Protein Structure, Tertiary
D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis