MucD regulates alginate biosynthesis through the proteolytic control of AlgX and AlgK in Pseudomonas aeruginosa
- 1School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
- 2NTU Institute of Structural Biology, Nanyang Technological University, Singapore, Singapore
Abstract
Pseudomonas aeruginosa is an opportunistic human pathogen capable of infecting a wide range of tissues and organs. Its persistence during chronic infection is strongly associated with biofilm formation, which depends on extracellular polysaccharides such as alginate. The HtrA-like periplasmic serine protease MucD is a key regulator of bacterial virulence, stress response, and alginate production, yet its molecular mechanism has remained largely unclear. Here, we discovered the alginate acetylation and export proteins AlgX and AlgK as MucD substrates, and characterized their degradation by mass spectrometry and bioinformatic analysis. We further determined the cryo-EM structure of MucD bound to an AlgK-derived substrate peptide, offering atomic insights into MucD oligomerization assembly, substrate recognition, and specificity. Together with structure-guided mutagenesis and biochemical assays, our results revealed that MucD proteolytic activity is governed by an equilibrium between a resting 12-mer and an active trimer. Crucially, we demonstrate that MucD represses alginate biosynthesis post-translationally, in addition to its previously implicated role in transcriptional regulation. These findings define a distinct activation mechanism and regulatory function for MucD and provide new insight into bacterial HtrA-like serine proteases.
The persistence of Pseudomonas aeruginosa during chronic infection relies on alginate production, a process regulated by the serine protease MucD. This study identifies the alginate acetylation and export proteins AlgX and AlgK as MucD substrates and shows that MucD proteolytic activity is regulated by oligomerization.
Versions
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BibTeX
@article{jiang2026mucd,
title = {{MucD regulates alginate biosynthesis through the proteolytic control of AlgX and AlgK in Pseudomonas aeruginosa}},
author = {Yujun Jiang and Xin-Fu Yan and Rya Ero and Chao Wang and Kanaga Sabapathy and Yong-Gui Gao},
journal = {PLOS Biology},
year = {2026},
month = sep,
doi = {10.1371/journal.pbio.3003985},
url = {https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3003985},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - MucD regulates alginate biosynthesis through the proteolytic control of AlgX and AlgK in Pseudomonas aeruginosa
AU - Yujun Jiang
AU - Xin-Fu Yan
AU - Rya Ero
AU - Chao Wang
AU - Kanaga Sabapathy
AU - Yong-Gui Gao
PY - 2026
DA - 2026/09/21
JO - PLOS Biology
DO - 10.1371/journal.pbio.3003985
UR - https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3003985
AB - Pseudomonas aeruginosa is an opportunistic human pathogen capable of infecting a wide range of tissues and organs. Its persistence during chronic infection is strongly associated with biofilm formation, which depends on extracellular polysaccharides such as alginate. The HtrA-like periplasmic serine protease MucD is a key regulator of bacterial virulence, stress response, and alginate production, yet its molecular mechanism has remained largely unclear. Here, we discovered the alginate acetylation and export proteins AlgX and AlgK as MucD substrates, and characterized their degradation by mass spectrometry and bioinformatic analysis. We further determined the cryo-EM structure of MucD bound to an AlgK-derived substrate peptide, offering atomic insights into MucD oligomerization assembly, substrate recognition, and specificity. Together with structure-guided mutagenesis and biochemical assays, our results revealed that MucD proteolytic activity is governed by an equilibrium between a resting 12-mer and an active trimer. Crucially, we demonstrate that MucD represses alginate biosynthesis post-translationally, in addition to its previously implicated role in transcriptional regulation. These findings define a distinct activation mechanism and regulatory function for MucD and provide new insight into bacterial HtrA-like serine proteases. The persistence of Pseudomonas aeruginosa during chronic infection relies on alginate production, a process regulated by the serine protease MucD. This study identifies the alginate acetylation and export proteins AlgX and AlgK as MucD substrates and shows that MucD proteolytic activity is regulated by oligomerization.
SN - 1545-7885
ER -