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Articles

A Phytotoxic Glycopeptide from Cultures of Corynebacterium insidiosum¹

^a Department of Botany and Microbiology, Montana State University, Bozeman, Montana 59715

Cultures of Corynebacterium insidiosum produce an extra-cellular phytotoxic glycopeptide that possesses the ability to wilt plant cuttings. Wilt induced by this glycopeptide is directly dependent upon time and upon concentration with measureable wilt occurring in 40 nM solutions in 1 hour. The organism produces 1.3 grams toxin/liter of culture medium. The toxin was purified, and the physical, chemical, and biological properties were measured. The glycopeptide has an empirical formula of C₁₀₈H₂₂₆O₁₃₂N based on 1 atom of nitrogen. The molecular weight as estimated by light scattering and column gel chromatography indicated values approximating 5 x 10⁶. The toxin does not dissociate into small molecular weight subunits when treated with 8 M urea or 30% pyridine.

The toxin has a specific optical rotation of []_{5460 Å}^{34.5 C} = –166°, an intrinsic viscosity of 0.2307 dl/g, and decomposes at 260 C. It has a blue chromophore due to copper chelation at a concentration of 75 moles copper/mole toxin. Mannose, glucose, galactose and L-fucose, with trace amounts of rhamnose and an unidentified reducing sugar, comprise 83.1% of the toxin. An unknown organic acid appearing chemically similar to a keto-deoxy organic acid comprises 8.8% of the toxin. Lysine₂, arginine₁, aspartic acid₁, threonine₁, serine₁, glutamic acid₁, glycine₂, alanine₂, valine₂, leucine₂, and isoleucine₁, form a single peptide with glycine as the sole NH₂-terminal amino acid. The peptide-carbohydrate linkage appears to be of a glycosidic nature involving the –OH of threonine. This single peptide composes 2.6% of the toxin, and there are 77 moles peptide/mole of purified glycopeptide.

³ Public Health Service Research Career Development Awardee 1-K4-GM-42, 475-02 from the National Institute of General Medical Sciences.

¹ This study was supported in part by National Science Foundation Grant GB-12956 and the Montana Agricultural Experiment Station, Station Paper No. 269, Journal Series.