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Truncated type IV pilin PilA108 activates the intramembrane protease AlgW to cleave MucA and PilA108 itself in vitro

Li, Ronghui, Withers, Ryan T., Dai, Jingcheng, Ruan, Jing, Li, Wei, Dai, Yujun, An, Weixing, Yu, Dianzhen, Wei, Hehong, Xia, Ming, Tian, Chunyuan, Yu, Hongwei D., Qiu, Dongru
Archives of microbiology 2016 v.198 no.9 pp. 885-892
Pseudomonas aeruginosa, genes, models, point mutation, polypeptides, protein synthesis, proteinases
For alginate production in Pseudomonas aeruginosa, the intramembrane protease AlgW must be activated to cleave the periplasmic domain of anti-sigma factor MucA for release of the sequestered ECF sigma factor AlgU. Previously, we reported that three tandem point mutations in the pilA gene, resulting in a truncated type IV pilin termed PilA¹⁰⁸ with a C-terminal motif of phenylalanine–threonine–phenylalanine (FTF), induced mucoidy in strain PAO579. In this study, we purified PilA¹⁰⁸ protein and synthesized a peptide ‘SGAGDITFTF’ corresponding to C-terminus of PilA¹⁰⁸ and found they both caused the degradation of MucA by AlgW. Interestingly, AlgW could also cleave PilA¹⁰⁸ between alanine⁶² and glycine⁶³ residues. Overexpression of the recombinant FTF motif-bearing MucE protein, originally a small periplasmic polypeptide with the C-terminal motif WVF, could induce mucoid conversion in the PAO1 strain. In all, our results provided a model of activation of AlgW by another protein ending with proper motifs. Our data suggest that in addition to MucA cleavage, AlgW may cleave other substrates.