Structural Basis of Trypsin Inhibition and Entomotoxicity of Cospin, Serine Protease Inhibitor Involved in Defense of Coprinopsis cinerea Fruiting Bodies

Abstract

Background: Mushrooms are a rich source of novel proteins with unique features. Results: Cospin, a trypsin-specific protease inhibitor, has a ␤-trefoil fold and is toxic against the fruit fly. Conclusion: Cospin represents one type of fungal protein-mediated defense against fungivorous insects. Significance: Cospin, the first fungal trypsin inhibitor with determined three-dimensional structure, utilizes a different loop for trypsin inhibition compared with other ␤-trefoil inhibitors.

Biotin-Binding Proteins in the Defense of Mushrooms against Predators and Parasites

“…Such a "patchy" distribution is typical for genes that are not involved in conserved physiological processes but rather function in biotic and abiotic interactions. Accordingly, the same type of distribution is observed for the genes coding for fungal defense lectins and protease inhibitors (5,20). In conclusion, we propose that cytoplasmic biotin-binding proteins constitute a novel class of effector proteins in fungal resistance and/or defense against antagonists.…”

“…A similar role has recently been proposed for fungal lectins (5) and protease inhibitors (20). Besides their toxicity, these proteins share other features, e.g., the lack of a signal sequence for classical secretion, their low molecular weight, their resistance to oxidation, high temperature, and proteolysis, and their abundant expression in fruiting bodies.…”

“…Such an antinutritional mechanism has also been proposed for protease inhibitors functioning as fungal defense proteins. These proteins are believed to inhibit gut proteases of fungivores necessary to digest ingested proteins (20). Fungal defense lectins, on the other hand, function in a more direct way.…”

“…Biotoxicity of the fungal BBPs was assessed by feeding the recombinant E. coli cells to C. elegans and Acanthamoeba sp. as previously described (15,20) and by adding purified recombinant tamavidin 2 to the rearing medium of D. melanogaster as described in Method S3 in the supplemental material and in reference 21.…”

A thermostable trypsin inhibitor with antiproliferative activity from small pinto beans

“…It is unique in that it has a blocked N-terminus since in our experience this is the only trypsin inhibitor that we have isolated with such a characteristic. Trypsin inhibitors are also present in animals 40,41 , fungi 42 and bacteria 43 . They all serve a defense function.…”