Isolation and molecular characterization of novel monomeric fungal subtilisin inhibitor from a plant pathogenic fungus, Choanephora cucurbitarum.

Isolation and molecular characterization of novel monomeric fungal subtilisin inhibitor from a plant pathogenic fungus, Choanephora cucurbitarum. Appl Environ Microbiol. 2020 Sep 04;: Authors: Pathiraja D, Chun Y, Cho JH, Min B, Lee S, Park H, Byun J, Choi IG Abstract The bacterial protease inhibitor domain, Streptomyces subtilisin inhibitor (SSI), is rarely found in fungi. Genome analysis of a fungal pathogen, Choanephora cucurbitarum KUS-F28377, revealed 11 SSI-like domains that are horizontally transferred and sequentially diverged during evolution. We investigated the molecular function of fungal SSI-like domains of C. cucurbitarum, designated as 'Choanepins'. Among the tested proteins, only choanepin9 showed inhibitory activity against subtilisin as the target protease, and accounting for 47% of the inhibitory activity of bacterial SSI. However, the binding affinity (Kd) of choanepin9 measured via microscale thermophoresis was 21 nM compared with 34 nM of bacterial SSI. The trend of binding and inhibitory activity suggests that the two inhibitors exhibit different inhibitory mechanism for subtilisin protease. Interestingly, choanepin9 was identified as a monomer in studies in vitro, whereas bacterial SSI is a homodimer. Based on the observations, we constructed a monomeric bacterial SSI protein with decreased binding affinity to abrogate the inhibitory activity. By altering the reactive sites of choanepin9 deduced from the P1 an...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research