The presence of glycoproteins in bacteria is very rare and virtually nothing is known about the mechanisms of protein glycosylation in Gram positive bacteria. The protein crystals produced by strains of Bacillus thuringiensis which can be larvicidal for Lepidoptera and Diptera insects have recently been characterized. The crystals are glycoprotein toxins containing roughly 3% covalently bound sugars. These sugars, which include both neutral sugars and aminosugars, contribute markedly to the crystal's biological activity. The present proposal (i) identifies the oligosaccharide structures from 4 different B. thuringiensis crystals including representatives of Lepidoptera- active and Diptera-active toxins; (ii) determines the peptide sequence (Asn - X - Ser/Thr??) of the oligosaccharide attachment sites; and (iii) determines the pathways for oligosaccharide synthesis and attachment in bacteria. The carbohydrate structure determinations are done in collaboration with the Complex Carbohydrate Research Center at the University of Georgia. The Bacillus bacteria produce protein crystals that are toxic to various insect larvae. The crystals are glycoproteins containing about 3% sugar. The sugar residues play an important role in the crystal's toxicity. Glycoproteins such as these are uncommon in bacteria, and little is known about their synthesis by these organisms. This research explores the structure and function of the sugar portions of glycoprotein toxins in Bacillus. The long term goals are to enhance and broaden insect toxicity. This could lead to the development of novel glycoprotein insecticides effective against previously nonsusceptible insects, such as houseflies, mites and ticks.
