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A tailored phosphoaspartate probe unravels CprR as a response regulator in Pseudomonas aeruginosa interkingdom signaling

ABSTRACT: Pseudomonas aeruginosa is a difficult-to-treat Gram-negative bacterial pathogen causing life-threatening infections. Adaptive resistance (AR) to cationic peptide antibiotics such as polymyxin B impairs the therapeutic success. This self-protection is mediated by two component systems (TCS) consisting of a membrane-bound histidine kinase and an intracellular response regulator (RR). As phosphorylation of the key RR aspartate residue is transient during signaling and hydrolytically unstable, the study of these systems is challenging. Therefore, we applied a tailored reverse polarity chemical proteomic strategy to capture this transient modification and read-out RR phosphorylation in complex proteomes using a nucleophilic probe. An ideal trapping methodology was developed with a recombinant RR demonstrating the importance of fine-tuned acidic pH values to facilitate the attack on the aspartate carbonyl C-atom and prevent unproductive hydrolysis. Analysis of Bacillus subtilis and P. aeruginosa proteomes revealed the detection of multiple phosphoaspartate sites, which closely resembled the conserved RR sequence motif. With this validated strategy we dissected the signaling of dynorphin A, a human peptide stress hormone, which is sensed by P. aeruginosa to mediate AR. Intriguingly, our methodology identified CprR as an unprecedented RR in dynorphin A interkingdom signaling.

INSTRUMENT(S): Q Exactive Plus

ORGANISM(S): Escherichia Coli Pseudomonas Aeruginosa Pao1 Bacillus Subtilis

SUBMITTER: Patrick Allihn

LAB HEAD: Stephan Axel Sieber

PROVIDER: PXD022426 | Pride | 2021-02-16

REPOSITORIES: Pride

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Project description:Unprecedented bacterial targets are urgently needed for the development of novel antibiotics to overcome the current resistance crisis. Challenges include the limited uptake of compounds as well as prioritizing proteins for their druggability and functional relevance. Especially, the wealth of uncharacterized proteins represents an untapped source for novel targets. However, tools to decipher their function are largely lacking. We here utilize the systematic mining of pyridoxal phosphate dependent enzymes (PLP DEs) in bacteria to focus on a target class, which is known to bind ligands, accesses PLP via active transport from the media and is involved in crucial metabolic processes. For this, we systematically exploited the chemical space of the pyridoxal (PL) scaffold and obtained eight PL probes bearing modifications at various ring positions. These probes were subsequently tested for phosphorylation by cognate kinases and labelling of PLP DEs in clinically relevant Gram-positive (Staphylococcus aureus) as well as Gram-negative (Escherichia coli and Pseudomonas aeruginosa) strains. Overall, the coverage of this diverse set of probes along with refined labelling conditions not only exceeded the performance of a previous probe generation, it also provided a detailed map of binding preferences of certain structural motifs. Although originally conducted in mutant cells devoid of PLP de novo biosynthesis, we here demonstrate efficient PLP DE labelling also in a wild type strain. Overall, the profiling revealed several putative PLP DEs with unknown function, of which we exemplarily characterized five via in-depth enzymatic assays. Finally, we screened a panel of putative PLP binders for antibiotic activity and unravelled the targets of hit molecules via competitive profiling with our probes. Here, an uncharacterized enzyme, essential for bacterial growth, was assigned as PLP dependent cysteine desulfurase and confirmed to be inhibited by the marketed drug phenelzine. Our approach provides a basis for deciphering novel PLP DEs as essential antibiotic targets along with corresponding ways to decipher small molecule inhibitors.

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	181103_SMH_181031_PA3.raw	Raw
	190421_PA_190411_1.raw	Raw
	190421_PA_190411_2.raw	Raw
	190421_PA_190411_3.raw	Raw
	190421_PA_190411_4.raw	Raw

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A tailored phosphoaspartate probe unravels CprR as a response regulator in Pseudomonas aeruginosa interkingdom signaling

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