Insect apolipophorin III. Purification and properties

Area of Science:

• Insect Biochemistry
• Lipoprotein Metabolism

Background:

• Adult Manduca sexta hemolymph contains a 17,000-dalton protein.
• This protein is scarce in larval hemolymph and does not bind larval lipophorin.

Purpose of the Study:

• To characterize the 17,000-dalton hemolymph protein from adult Manduca sexta.
• To investigate its association with lipophorin and its biochemical properties.

Main Methods:

• Guanidinium chloride treatment to dissociate the protein from lipophorin.
• Purification using gel permeation, ion exchange, and lectin chromatography.
• Analysis of isoelectric point, amino acid composition, and dimerization.

Main Results:

• The protein, designated apolipophorin III, associates with adult lipophorin.
• Apolipophorin III is a non-glycosylated polypeptide, lacking cysteine and tryptophan.
• The 17,000-dalton polypeptide dimerizes to form a 34,000-dalton protein in solution.

Conclusions:

• Apolipophorin III is a distinct protein component of adult Manduca sexta hemolymph.
• Its properties suggest a role in adult lipoprotein function.
• Further research is needed to elucidate its specific biological function.