Structural insights into regulated intramembrane proteolysis by the positive alginate regulator MucP from Pseudomonas aeruginosa

• Published in: Biochemical and biophysical research communications 2024-12, Vol.740, p.150999, Article 150999
• Main Authors: Lou, Xiaorui, Li, Shanshan, Wang, Yanan, Wang, Runhao, Li, Weiping, Yan, Jiaqi, Zhang, Qionglin, Liu, Ruihua, Bartlam, Mark
• Format: Article
• Language: English
• Subjects: Alginate biosynthesis; Alginates - chemistry; Alginates - metabolism; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Biofilms - growth & development; Cell Membrane - metabolism; Crystallography, X-Ray; Models, Molecular; MucP; PDZ domain; PDZ Domains; Protein Binding; Protein Conformation; Proteolysis; Pseudomonas aeruginosa; Pseudomonas aeruginosa - metabolism; Regulated intramembrane proteolysis; Sigma Factor - chemistry; Sigma Factor - metabolism
• ISSN: 0006-291X; 1090-2104; 1090-2104
• DOI: 10.1016/j.bbrc.2024.150999

Regulated intramembrane proteolysis (RIP) is a fundamentally conserved mechanism involving sequential cleavage by a membrane-bound Site-1 protease (S1P) and a transmembrane Site-2 protease (S2P). In the opportunistic pathogen Pseudomonas aeruginosa, the alternate sigma factor σ22 activates alginate production and in turn is regulated by the MucABCD system. The anti-sigma factor MucA, which inhibits σ22, is sequentially cleaved via RIP by AlgW (S1P) and MucP (S2P) respectively. In this study, we report high-resolution crystal structures of the MucP PDZ1 and PDZ2 domains. Structural and binding analysis confirms that MucP PDZ2 recognizes the carboxy-terminal Ala136 residue of MucA following Site-1 cleavage by AlgW, while the peptide binding groove of PDZ1 is obstructed by a short α-helix. A structure of MucP PDZ2 with bound MucA peptide shows how PDZ2 binds the newly exposed carboxyl terminus of MucA following AlgW cleavage. The ability of a ΔmucP strain of P. aeruginosa to form biofilms was reduced to a similar extent as a ΔalgW strain. This work paves the way for further studies of MucP and other PDZ-containing S2Ps in regulated intramembrane proteolysis. •Crystal structures of P. aeruginosa MucP PDZ1 and PDZ2 domains were determined.•The peptide binding groove of MucP PDZ1 is occluded by an α-helix.•The peptide binding groove of MucP PDZ2 is unobstructed.•A MucP PDZ2-peptide structure shows how it recognizes MucA after cleavage by AlgW.•ΔmucP impairs P. aeruginosa biofilm formation to a similar degree as ΔalgW.