Department of Biochemistry and Molecular and Structural Biology, Jožef Stefan Institute, 1000 Ljubljana, Slovenia.
Department of Biotechnology, Jožef Stefan Institute, 1000 Ljubljana, Slovenia.
Int J Mol Sci. 2022 Apr 28;23(9):4916. doi: 10.3390/ijms23094916.
We introduce a new family of fungal protease inhibitors with β-trefoil fold from the mushroom , named cocaprins, which inhibit both cysteine and aspartic proteases. Two cocaprin-encoding genes are differentially expressed in fungal tissues. One is highly transcribed in vegetative mycelium and the other in the stipes of mature fruiting bodies. Cocaprins are small proteins (15 kDa) with acidic isoelectric points that form dimers. The three-dimensional structure of cocaprin 1 showed similarity to fungal β-trefoil lectins. Cocaprins inhibit plant C1 family cysteine proteases with in the micromolar range, but do not inhibit the C13 family protease legumain, which distinguishes them from mycocypins. Cocaprins also inhibit the aspartic protease pepsin with in the low micromolar range. Mutagenesis revealed that the β2-β3 loop is involved in the inhibition of cysteine proteases and that the inhibitory reactive sites for aspartic and cysteine proteases are located at different positions on the protein. Their biological function is thought to be the regulation of endogenous proteolytic activities or in defense against fungal antagonists. Cocaprins are the first characterized aspartic protease inhibitors with β-trefoil fold from fungi, and demonstrate the incredible plasticity of loop functionalization in fungal proteins with β-trefoil fold.
我们从蘑菇中介绍了一个具有β-三叶折叠结构的新型真菌蛋白酶抑制剂家族，名为 cocaprins，它可以抑制半胱氨酸蛋白酶和天冬氨酸蛋白酶。两种 cocaprin 编码基因在真菌组织中差异表达。一种在营养菌丝中高度转录，另一种在成熟子实体的菌柄中转录。Cocaprins 是小蛋白（15 kDa），具有酸性等电点，可形成二聚体。cocaprin 1 的三维结构与真菌 β-三叶折叠凝集素相似。Cocaprins 以微摩尔范围抑制植物 C1 家族半胱氨酸蛋白酶，但不抑制 C13 家族蛋白酶 legumain，这使它们与 mycocypins 区别开来。Cocaprins 还以低微摩尔范围抑制天冬氨酸蛋白酶胃蛋白酶。突变分析表明，β2-β3 环参与半胱氨酸蛋白酶的抑制，天冬氨酸蛋白酶和半胱氨酸蛋白酶的抑制反应位点位于蛋白质的不同位置。它们的生物学功能被认为是调节内源性蛋白水解活性或抵御真菌拮抗物。Cocaprins 是第一个从真菌中鉴定出的具有β-三叶折叠结构的天冬氨酸蛋白酶抑制剂，展示了真菌中具有β-三叶折叠结构的蛋白质中环功能化的令人难以置信的可塑性。
