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Submitted to: American Society for Microbiology
Publication Type: Abstract Only Publication Acceptance Date: 4/12/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Fungal entomopathogens like Beauveria bassiana are being used as biological control agents for a variety of insect pests. Extracelluar proteases produced by fungal entomopathogens are important virulence factors because they play a major role in insect cuticle penetration. In this study an extracellular protease was obtained from a B. bassiana isolate cultured from an infected rice water weevil (Lissorhoptrus oryzophilus). The protease is distinct from previously described proteases obtained from B. bassiana. The protease was produced when cells growing in liquid gelatin media reached stationary phase. A combination of ion exchange and gel filtration chromatography was used to purify the protease. Various characteristics of the protease were examined along with a purified preparation of Pr1, a key extracellular protease involved in cuticle penetration. Like Pr1, the newly isolated protease is inhibited by phenylmethylsulfonyl fluoride indicating that it is a serine protease. The protease also exhibits a preference for the chymotrypsin substrate N-succin a-Ala-Pro-Phe p-nitroanilide, as does Pr1. Based on SDS-PAGE, the newly isolated protease is slightly smaller (MW = 31.5 kDA) than Pr1 (MW = 32 kDA). It also has an isoelectric point (pI = 7.5) much lower than that of Pr1 (pI > 9.6). Furthermore, unlike Pr1, the newly isolated protease is not produced in basal salts media containing cotton boll weevil (Anthonomus grandis grandis) cuticle. This suggests that the proteinase may not be involved in insect cuticle degradation and leaves in question its biological role. |
