Purification, characterization, and analysis of antibacterial activity of a serum lectin from the grub of rhinoceros beetle, Oryctes rhinoceros

[Display omitted] •Galactose specific lectin was purified in the grub serum of rhinoceros beetle.•Purified lectin was a 213kDa protein with three polypeptide subunits.•Purified lectin possess both bacterial agglutination and antibacterial activities. Lectins, also recognized as hemagglutinins, are multivalent proteins, and their desirable quality of fine sugar-binding specificity plays an important role in defense functions in invertebrates. In the present study, a galactose-specific lectin was detected, purified, and characterized from the hemolymph of the grub of rhinoceros beetle, Oryctes rhinoceros. The lectin was purified by affinity column chromatography with acid-treated Sepharose 6B as the matrix. The purified lectin was heat-labile, cation independent, and insensitive to EDTA. It revealed the presence of three distinct polypeptides with molecular weights of 90, 78, and 45kDa. Thus, the native molecular weight of the purified lectin was calculated to be approximately 213kDa, as revealed by a single band in native-PAGE. Studies on antibacterial activity and bacterial agglutination assays revealed that the purified lectin possess both these properties against two bacterial species, Bacillus subtilis and B. pumilus, isolated from the native larval habitat of O. rhinoceros.