摘要
The snowdrop lectin GNA （Galanthus nivalis agglutinin） has been shown to possess insecticidal activity to a range of economically important insect pests. However, the precise mechanism of insecticidal action of GNA against insects remains unknown. In this investigation, we attempted to purify and identify receptor（s） responsible for binding of GNA in the larval midgut of a major lepidopteran pest （the cotton leafworm, Spodoptera littoralis） to better understand its mode of action. Therefore, cytoplasmic as well as membrane proteins from 800 larval midguts were chromatographed on a column with immobilized GNA. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the proteins eluted from the GNA column followed by sequencing of the GNA-binding proteins and BLAST analyses revealed that the N-terminal sequences of a 24 kDa polypeptide purified from the cytoplasmic and membrane protein fraction revealed sequence similarity to sequences encoding heavy chain homologs of ferritin from Manduca sexta （76% sequence identity）, Calpodes ethlius （80% sequence identity） and Bombyx mori （61% sequence identity）. Furthermore, the N-terminal sequence of a 31 kDa polypeptide from the membrane protein fraction showed sequence similarity to a light chain homolog of ferritin from Manduca sexta （88% sequence identity）.
The snowdrop lectin GNA （Galanthus nivalis agglutinin） has been shown to possess insecticidal activity to a range of economically important insect pests. However, the precise mechanism of insecticidal action of GNA against insects remains unknown. In this investigation, we attempted to purify and identify receptor（s） responsible for binding of GNA in the larval midgut of a major lepidopteran pest （the cotton leafworm, Spodoptera littoralis） to better understand its mode of action. Therefore, cytoplasmic as well as membrane proteins from 800 larval midguts were chromatographed on a column with immobilized GNA. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the proteins eluted from the GNA column followed by sequencing of the GNA-binding proteins and BLAST analyses revealed that the N-terminal sequences of a 24 kDa polypeptide purified from the cytoplasmic and membrane protein fraction revealed sequence similarity to sequences encoding heavy chain homologs of ferritin from Manduca sexta （76% sequence identity）, Calpodes ethlius （80% sequence identity） and Bombyx mori （61% sequence identity）. Furthermore, the N-terminal sequence of a 31 kDa polypeptide from the membrane protein fraction showed sequence similarity to a light chain homolog of ferritin from Manduca sexta （88% sequence identity）.
