| Title | Mutational analysis on stable expression and LasB inhibition of LasB propeptide in Pseudomonas aeruginosa |
|---|---|
| Author | Youngsun Shin, Xi-Hui Li, Cheol Seung Lee, and Joon-Hee Lee* |
| Address | Department of Pharmacy, College of Pharmacy, Pusan National University, Busan 46241, Republic of Korea |
| Bibliography | Journal of Microbiology, 60(7),727-734, 2022, |
| DOI | 10.1007/s12275-022-1671-5 |
| Key Words | Pseudomonas aeruginosa, elastase, LasB, propeptide, protease, protease inhibition, protein stability |
| Abstract | Three major proteases, elastase B (LasB), protease IV (PIV), and elastase A (LasA) expressed in Pseudomonas aeruginosa play important roles in infections and pathogeneses. These are activated by a proteolytic cascade initiated by the activation of LasB. In this study, we investigated whether LasB could be inhibited using its propeptide (LasBpp). Although LasA and PIV were inhibited by their propeptides, LasB was not inhibited by purified LasBpp because LasB degraded LasBpp. To address this problem, mutant LasBpp variants were constructed to obtain a mutant LasBpp resistant to LasB degradation. A C-terminal deletion series of LasBpp was tested in vivo, and two positive candidates, T2 and T2-1, were selected. However, both caused growth retardation and were unstably expressed in vivo. Since deleting the C-terminal end of LasBpp significantly affected its stable expression, substitution mutations were introduced at the two amino acids near the truncation site of T2-1. The resulting mutants, LasBppE172D, LasBppG173A, and LasBppE172DG173A, significantly diminished LasB activity when overexpressed in vivo and were stably expressed in MW1, a quorum sensing mutant that does not produce LasB. In vitro analysis showed that purified LasBppE172DG173A inhibited LasB activity to a small extent. Summarizing, Cterminal modification of LasBpp profoundly affected the stable expression of LasBpp, and little enhanced the ability of LasBpp to resist degradation by LasB. |