A toxic protein, hirsutellin A, has been purified from the mite fungal pathogen, Hirsutella thompsonii, using ammonium sulphate precipitation, ion exchange chromatography and gel filtration on BiolGel P-10. The protein has been characterized as a monomer with a molecular mass of 15 kDa and an isoelectric point of 10.5. The amino acid composition and the N-terminal sequence of hirsutellin A (34 amino acids) have been determined. From these results, the toxin appears to be distinct from other known proteins. It is not glycosylated, and does not show proteolytic activity. The toxin is also antigenic, thermostable and not inactivated by treatments with proteolytic enzymes. Toxicity bioassays showed that injection of larvae of the waxmoth, Galleria mellonella, with hirsutellin A at low dosages [I pg toxin (g body wt)-l] caused a high mortality rate. Hirsutellin A was also toxic per 0s to neonatal larvae of the mosquito Aedes aegypti.
Abstract. Highly active metabolites have been detected in the hemolymph of the lepidopteran Spodoptera exigua infected with the mycopathogen, Beauveria bassiana. A combination of phenyl sepharose and CM ion exchange chromatography was utilized to extract the active metabolites from infected hemolymph samples. The active in vivo metabolites, having a molecular mass greater than 10 KDa, were thermolabile and were inactivated by proteinase K. These metabolites were characterized by their ability to disrupt metamorphosis, killing treated larvae at the wandering or pupal stage. Additionally, injection of S. exigua larvae with 'active' samples caused a reduction in the number of filopodial-producing hemocytes. The biological activities and biochemical properties suggest that novel compounds are produced during B. bassiana mycosis.
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