SlyB encapsulates outer membrane proteins in stress-induced lipid nanodomains

• Published in: Nature (London) 2024-02, Vol.626 (7999), p.617-625
• Main Authors: Janssens, Arne, Nguyen, Van Son, Cecil, Adam J., Van der Verren, Sander E., Timmerman, Evy, Deghelt, Michaël, Pak, Alexander J., Collet, Jean-François, Impens, Francis, Remaut, Han
• Format: Article
• Language: English
• Subjects: 101/28; 14/63; 631/326/41/2180; 631/326/41/2536; 631/45/287/1191; 631/535/1258/1259; 631/57/2271; 82; 82/1; 82/29; 82/58; 82/83; Antimicrobial peptides; Asymmetry; Bacteria; Bacterial Outer Membrane Proteins - chemistry; Binding sites; Cell Membrane - metabolism; Destabilization; E coli; Encapsulation; Escherichia coli Proteins - metabolism; Glycine; Gram-negative bacteria; Humanities and Social Sciences; Integrity; Lipids; Lipopolysaccharides; Lipopolysaccharides - chemistry; Lipopolysaccharides - pharmacology; Lipoproteins; Lipoproteins - analysis; Lipoproteins - metabolism; Membrane proteins; Membranes; multidisciplinary; Oligomerization; Outer membrane proteins; Pathogens; Peptides; Phosphates; Phospholipids; Proteins; Proteomes; Science; Science (multidisciplinary)
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-023-06925-5

The outer membrane in Gram-negative bacteria consists of an asymmetric phospholipid—lipopolysaccharide bilayer that is densely packed with outer-membrane β-barrel proteins (OMPs) and lipoproteins 1 . The architecture and composition of this bilayer is closely monitored and is essential to cell integrity and survival 2 – 4 . Here we find that SlyB, a lipoprotein in the PhoPQ stress regulon, forms stable stress-induced complexes with the outer-membrane proteome. SlyB comprises a 10 kDa periplasmic β-sandwich domain and a glycine zipper domain that forms a transmembrane α-helical hairpin with discrete phospholipid- and lipopolysaccharide-binding sites. After loss in lipid asymmetry, SlyB oligomerizes into ring-shaped transmembrane complexes that encapsulate β-barrel proteins into lipid nanodomains of variable size. We find that the formation of SlyB nanodomains is essential during lipopolysaccharide destabilization by antimicrobial peptides or acute cation shortage, conditions that result in a loss of OMPs and compromised outer-membrane barrier function in the absence of a functional SlyB. Our data reveal that SlyB is a compartmentalizing transmembrane guard protein that is involved in cell-envelope proteostasis and integrity, and suggest that SlyB represents a larger family of broadly conserved lipoproteins with 2TM glycine zipper domains with the ability to form lipid nanodomains. SlyB, a lipoprotein in the PhoPQ stress regulon in Gram-negative bacteria, forms stable stress-induced complexes with the outer membrane proteome.