Phosphorylation enhances structural adaptability of Fap proteins: a proteomics and bioinformatics approach

The complex regulatory network of proteins in Pseudomonas aeruginosa controls pathogenesis and cellular sustainability. Phosphorylation in Pseudomonas play a central role in this regulation. Functional amyloids in Pseudomonas (Fap) expression influences the global proteome, suggesting its influence on the protein-interaction network. The preliminary exploration of Fap interactome through immunoprecipitation/mass spectrometry (IP/MS) were enriched for phosphokinase proteins. This called forth for phosphoproteomics which revealed three proteins of the Fap operon, FapD, FapB, and FapF were found in multi-phosphorylated state. In silico phosphorylation at experimentally determined positions of Fap protein structures provided insight into structural changes. Phosphorylation of FapD reinforces protein-protein interaction ability by increasing protein binding residues and flexibility of interfacial domains. Phosphorylated FapB affects the stability of the aggregating core by regulating the exposure and flexibility of the aggregation-prone regions. FapF in the phosphorylated form displayed structural changes in regions that functionally assist transportation process. Multi-site phosphorylation can generate inter-/intra - regulon network that can explain how expression of Fap influences global proteome. Multisite phosphorylation of Fap proteins is tailored for specific protein modulations that can provide functional adaptability and assist successful amyloid biogenesis.