Lysine Polyphosphate Modification Regulates Enzymatic and Signaling Functions in Eukaryotic and Bacterial Systems

Polyphosphate (polyP) is a highly conserved inorganic polymer involved in diverse regulatory processes across all domains of life. In bacteria, polyP is synthesized primarily by polyphosphate kinase 1 (PPK1) and deletion of the ppk1 gene results in significant alterations in cellular physiology and virulence. In contrast, the mechanisms by which polyP regulates protein function in eukaryotic systems remains less well defined. We previously identified a post-translational modification termed Histidine Polyphosphate Modification (HPM), in which polyP associates with histidine-rich regions to influence protein function. Building on this finding, our laboratory subsequently reported a related modification, Lysine Polyphosphate Modification (KPM), occurring on proteins containing lysine-rich stretches. In this thesis, we conducted a functional analysis of a selected KPM target, N-myristoylation transferase 2 (NMT2). Using a fluorescence-based enzymatic assay, we observed that KPM of NMT2 reduces the release of myristoyl groups, consistent with partial inhibition of its catalytic activity. These results provide functional evidence that polyP association with lysine-rich regions can modulate enzyme activity in a mammalian context. In parallel, we investigated whether lysine-rich sequences could be exploited to perturb polyP-dependent processes in bacteria. Specifically, we examined whether a poly-K peptide could interfere with polyP-mediated virulence in Pseudomonas aeruginosa. Treatment with 1-10 µM of the poly-K peptide reduced the production of virulence factors including pyoverdine, motility, and biofilm formation. These findings suggest that lysine-rich peptides may function as polyP-neutralizing agents, attenuating polyP-dependent pathogenic traits. Collectively, this work reinforces the concept of polyP-associated protein modifications, establishes functional relevance for KPM in a defined mammalian enzyme, and explores the feasibility of targeting polyP-dependent mechanisms in bacterial pathogens.

Department dc:contributor.department

Biomedical and Molecular Sciences

Year dc:date.issued

2026

Author dc:creator

• Martins, Isabella

Advisor dc:contributor.supervisor

• Jia, Zongchao

• polyphosphate
• NMT2
• bacterial regulation
• virulence
• Pseudomonas aeruginosa
• myristoylation
• antibiotic resistance
• lysine repeats

Statement dc:rights

• Attribution 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by/4.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1974/36309

OAI identifier oai:identifier

oai:queensu.scholaris.ca:1974/36309