Evolution and Structure-Function Prediction of Eqolisins in Fungi

Background Botrytis cinerea is a phytopathogenic fungus that acidifies its environment (pH < 4), which has been shown to be related with the spectrum of secreted hydrolytic enzymes that are involved in the degradation of the host’s cell wall. Among these are about 20 proteases that belong to three protein families that are subject to functional redundancy and diversification. The eqolisins or glutamic peptidases (G1) form a novel family of acid endopeptidases and are encoded by four genes in B. cinerea. Point mutation analyses revealed its catalytic site is formed by a catalytic dyad (Q53, E136, hence the name eqolisin), the catalytic mechanism is known, and structures, including a structure with a transition state inhibitor, are available. The basic structure of eqolisins consists of two seven-stranded anti-parallel β-sheets which form a convex β-sandwich structure. It has two loops, the “beta loop” and the “70’s loop” which are likely involved in substrate interaction. Here we report a study on the evolution, and more particularly, the functional diversification of eqolisins in fungi.