Biology subjects

Reitzel, C.

Publications and source records attributed to Reitzel, C..

3 recordsLinked to original sources

bioRxiv2026

SbmA coordinates iron homeostasis and antimicrobial susceptibility in Klebsiella pneumoniae through phosphorylation-dependent regulation

Iron is an essential nutrient that underpins fundamental biological processes, yet its bioavailability is severely restricted during infection due to oxidation and host-mediated sequestration. In Gram-negative pathogens, such as Klebsiella pneumoniae, iron limitation imposes a critical selective pressure, necessitating tightly regulated acquisition systems to support growth, virulence, and survival. While canonical pathways for iron uptake are well characterized, regulatory mechanisms coordinating these processes remain incompletely understood. Here, we applied mass spectrometry-based phosphoproteomics to identify iron-responsive regulatory events associated with bacterial iron homeostasis. This approach revealed iron-dependent phosphorylation of SbmA, a conserved inner membrane transporter previously implicated in the uptake of antimicrobial peptides and related substrates. Functional characterization demonstrated that deletion of sbmA results in reduced intracellular iron levels and altered cellular morphology, supporting a role in iron acquisition. Complementary proteome mapping of {Delta}sbmA revealed compensatory production of siderophore receptors and TonB-dependent transport systems, further implicating SbmA in maintaining iron balance. Leveraging these findings, integration with high-throughput drug screening identified a compound that exploits SbmA-mediated transport to inhibit bacterial growth, highlighting its potential as a therapeutic entry point. Collectively, this work uncovers a previously unrecognized role for SbmA in iron homeostasis and demonstrates the power of phosphoproteomics to identify condition-specific regulators of essential bacterial pathways. These findings position SbmA as a promising target for antimicrobial development in K. pneumoniae.

microbiology↗

bioRxiv2026

Iron-responsive phosphorylation of TolQ modulates cell envelope integrity and antibiotic susceptibility in Klebsiella pneumoniae

Klebsiella pneumoniae is an opportunistic bacterial pathogen associated with high morbidity and mortality, exacerbated by the rapid emergence of resistance to last-resort antibiotics, such as carbapenems. Adaptation to nutrient limitation, particularly fluctuations in metal availability, is critical for bacterial survival and virulence, yet the regulatory mechanisms coordinating these responses remain incompletely understood. Protein phosphorylation represents a key post-translational modification governing bacterial physiology and offers a promising avenue for identifying novel antimicrobial targets. Here, we applied mass spectrometry-based phosphoproteomics to define nutrient-responsive signaling networks in K. pneumoniae under varying iron and zinc conditions. This analysis identified iron-dependent phosphorylation of TolQ, a conserved inner membrane component of the Tol-Pal system that maintains cell envelope integrity. Structural modeling predicted that phosphorylation modulates TolQ-TolR conformation, suggesting a mechanism by which iron availability regulates Tol-Pal function. Functional characterization demonstrated that deletion of tolQ results in reduced bacterial viability, increased susceptibility to host immune clearance, and heightened sensitivity to antibiotic treatment. To further explore the therapeutic potential of this pathway, we integrated high-throughput compound screening with computational modeling and identified small molecules that phenocopy {Delta}tolQ. Collectively, these findings reveal a previously unrecognized link between iron availability and phosphoregulation of the Tol-Pal system and establish TolQ as a critical mediator of bacterial survival. This work highlights phosphoproteomics as a powerful strategy to uncover regulatory vulnerabilities and identify targets for antimicrobial development in drug-resistant pathogens.

microbiology↗

bioRxiv2024

de Novo Sequencing of Antibodies for Identification of Neutralizing Antibodies in Human Plasma Post SARS-CoV-2 Vaccination

We present a method for sequencing polyclonal IgG enriched from human plasma, employing a combination of de novo sequencing, proteomics, bioinformatics, protein separation, sequencing, and peptide separations. Our study analyzes a single patients IgG antibody response triggered by the Moderna Spikevax mRNA COVID-19 vaccine. From the sequencing data of the natural polyclonal response to vaccination, we generated 12 recombinant antibodies. Six derived recombinant antibodies, including four generated with de novo sequencing, exhibited similar or higher binding affinities than the original natural polyclonal antibody. Our neutralization tests revealed that the six antibodies possess neutralizing capabilities against the target antigen. This research provides insights into sequencing polyclonal IgG antibodies while highlighting the effectiveness and potential of our approach in generating recombinant antibodies with robust binding affinity and neutralization capabilities. Our proposed approach is an advancement in characterizing the IgG response by directly investigating the circulating pool of IgG without relying exclusively on the B-cell repertoire or population. This is crucial as the B-cell analysis may not accurately represent the circulating antibodies. Interestingly, a large proportion (80 to 90%) of the human antibody sequences generated against SARS-CoV-2 in the literature have been derived solely from B-cell analysis. Therefore, the ability to offer a different perspective is crucial in gaining a comprehensive understanding of the IgG response. Significance StatementWe investigate human IgG targeting the receptor binding domain using de novo proteomics. The peripheral B-cell repertoire may not adequately cover all the circulating IgG for human IgG sequencing. Our approach overcomes this limitation by using a de novo protein sequencing on top of standard proteomics. We obtained distinct de novo sequences, showcasing our methods potential. The recombinant proteins we generate possess traits comparable to or surpassing the naturally occurring polyclonal antibodies (pAbs). This study highlights similarities and differences between IgG populations in blood and circulating B-cells, which is crucial for future biologics development.

immunology↗