Biology subjects

Cho, T. H. S.

Publications and source records attributed to Cho, T. H. S..

3 recordsLinked to original sources

bioRxiv2025

YfgH is a transmembrane glycine-zipper containing lipoprotein that stabilizes excess cardiolipin and outer membrane proteins during envelope stress

The outer membrane (OM) of Escherichia coli is an essential, asymmetric bilayer composed of lipopolysaccharide and phospholipids that protects cells from environmental stress. While several systems maintain OM integrity during stress, the roles of many outer membrane lipoproteins are less well characterized. Here, we identify YfgH, a glycine-zipper domain containing lipoprotein, as a novel OM-stabilizing factor that functions distinctly from the previously studied SlyB. Deletion of yfgH increases sensitivity to detergents and metal chelators, enhances OM permeability, and leads to global loss of OM proteins under stress. YfgH is essential for survival during CRISPR interference-mediated depletion of OM biogenesis genes, and its overexpression rescues these phenotypes. AlphaFold modeling predicts YfgH forms oligomeric ring-like structures similar to SlyB, but genetic suppressor screens indicate distinct mechanisms: clsA (cardiolipin synthase) mutations suppress yfgH deletion, while slyB suppressors map to the Mla lipid transport pathway. Biochemical analyses reveal YfgH interacts with multiple OM proteins, especially under stress. Together these findings suggest YfgH functions by stabilizing cardiolipin-rich nanodomains, representing a novel response to OM stress. This work expands our understanding of glycine-zipper lipoproteins as stress-specific membrane stabilizers and highlights the critical role of YfgH in preserving OM integrity during envelope perturbation. ImportanceThe bacterial outer membrane is essential for survival in harsh environments, yet how Gram-negative cells maintain its stability under stress remains less understood. We identify YfgH, a previously uncharacterized outer membrane lipoprotein, as a key factor that preserves membrane integrity during envelope stress. Our findings show that YfgH stabilizes cardiolipin-rich nanodomains and protects outer membrane proteins when biogenesis pathways are compromised. This work reveals a new mechanism of outer membrane maintenance and expands the functional repertoire of glycine zipper- containing lipoproteins, highlighting a broader family of stress-specific membrane stabilizers that may be conserved across Gram-negative bacteria.

molecular biology↗

bioRxiv2023

The sensor of the bacterial histidine kinase CpxA is a novel dimer of extracytoplasmic Per-ARNT-Sim (PAS) domains

Histidine kinases are key bacterial sensors that recognize diverse environmental stimuli. While mechanisms of phosphorylation and phosphotransfer by cytoplasmic kinase domains are relatively well-characterized, the ways in which extracytoplasmic sensor domains regulate activation remain mysterious. The Cpx envelope stress response is a conserved Gram-negative two-component system which is controlled by the sensor kinase CpxA. We report the structure of the Escherichia coli CpxA sensor domain (CpxA-SD) as a globular Per-ARNT-Sim (PAS)-like fold highly similar to that of Vibrio parahaemolyticus CpxA as determined by X-ray crystallography. Because sensor kinase dimerization is important for signaling, we used AlphaFold2 to model CpxA-SD in the context of its connected transmembrane domains, which yielded a novel dimer of PAS domains possessing a distinct dimer organization compared to previously characterized sensor domains. Gain of function cpxA* alleles map to the dimer interface, and mutation of other residues in this region also leads to constitutive activation. CpxA activation can be suppressed by mutations that restore inter-monomer interactions, suggesting that inhibitory interactions between CpxA-SD monomers are the major point of control for CpxA activation and signaling. Searching through hundreds of structural homologues revealed the sensor domain of Pseudomonas aeruginosa sensor kinase PfeS as the only PAS structure in the same novel dimer orientation as CpxA, suggesting that our dimer orientation may be utilized by other extracytoplasmic PAS domains. Overall, our findings provide insight into the diversity of the organization of PAS sensory domains and how they regulate sensor kinase activation. SignificanceBacterial two-component systems play an essential role in sensing environmental cues, mitigating stress, and regulating virulence. We approach the study of a key Gram-negative sensor kinase CpxA with both classical methods in structural biology and genetic analysis and emerging protein-folding prediction software. This approach provides a wholistic perspective on the structure and function of histidine kinases as proteins with modular and cellular compartment-spanning domain architectures. We report a novel organization of PAS domains in CpxA, highlighting the versatility and diversity of this sensory fold. Ultimately, these studies will facilitate the continued development of novel antimicrobials against sensor kinases, including CpxA, which is a previously studied target for antimicrobials.

molecular biology↗

bioRxiv2022

NlpE is an OmpA-associated outer membrane sensor of the Cpx envelope stress response

Gram-negative bacteria utilize several envelope stress responses (ESRs) to sense and respond to diverse signals within a multi-layered cell envelope. The CpxRA ESR responds to multiple stresses that perturb envelope protein homeostasis. Signaling in the Cpx response is regulated by auxiliary factors such as the outer membrane (OM) lipoprotein NlpE, an activator of the response. NlpE communicates adhesion to surfaces to the Cpx response; however, the mechanism by which NlpE accomplishes this remains unknown. In this study, we report a novel interaction between NlpE and the abundant OM protein OmpA. Both NlpE and OmpA are required to activate the Cpx response in surface-adhered cells. Furthermore, NlpE senses OmpA overexpression and the NlpE C-terminal domain transduces this signal to the Cpx response, revealing a novel signaling function for this domain. Overall, these findings reveal NlpE to be a versatile envelope sensor that takes advantage of its structure, localization, and cooperation with other envelope proteins to initiate adaptation to diverse signals. SignificanceThe envelope is not only a barrier that protects bacteria from the environment but also a crucial site for the transduction of signals critical for colonization and pathogenesis. The discovery of novel complexes between NlpE and OmpA contributes to an emerging understanding of the key contribution of complexes of {beta}-barrel proteins and lipoproteins to envelope stress signaling. Overall, our findings provide mechanistic insight into how the Cpx response senses signals relevant to surface adhesion and biofilm growth to facilitate bacterial adaptation.

microbiology↗