Acinetobacter baumannii, a Gram-negative opportunistic pathogen, is a leading cause of hospital-and communityacquired infections. Acinetobacter baumannii can rapidly acquire diverse resistance mechanisms and undergo genetic modifications that confer resistance and persistence to all currently used clinical antibiotics. In this study, we found exogenous L-lysine sensitizes Acinetobacter baumannii, other Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae) and a Gram-positive bacterium (Mycobacterium smegmatis) to aminoglycosides. Importantly, the combination of L-lysine with aminoglycosides killed clinically isolated multidrug-resistant Acinetobacter baumannii and persister cells. The exogenous L-lysine can increase proton motive force via transmembrane chemical gradient, resulting in aminoglycoside acumination that further accounts for reactive oxygen species production. The combination of L-lysine and antibiotics highlights a promising strategy against bacterial infection.

Protein phosphorylation plays a key role in Mycobacterium tuberculosis (Mtb) physiology and pathogenesis. We have previously shown that a secreted protein tyrosine phosphatase, PtpA, is essential for Mtb inhibition of host macrophage acidification and maturation, and is a substrate of the protein tyrosine kinase, PtkA, encoded in the same operon. In this study, we constructed a ∆ptkA deletion mutant in Mtb and found that the mutant exhibited impaired intracellular survival in the THP-1 macrophage infection model, correlated with the strain’s inability to inhibit macrophage phagosome acidification. By contrast, the mutant displayed increased resistance to oxidative stress in vitro. Proteomic and transcriptional analyses revealed upregulation of ptpA, and increased secretion of TrxB2, in the ΔptkA mutant. Kinase and protein-protein interaction studies demonstrated that TrxB2 is a substrate of PtkA phosphorylation. Taken together these studies establish a central role for the ptkA-ptpA operon in Mtb pathogenesis.

Edited by Zhijie Chang Keywords:Protein tyrosine kinase A Protein tyrosine phosphatase A Protein kinase A Phosphorylation Mycobacterium tuberculosis a b s t r a c t Protein tyrosine phosphatase A (PtpA) has been shown to play a key role in human macrophage infection by Mycobacterium tuberculosis (Mtb). Protein tyrosine kinase A (PtkA) was the first protein tyrosine kinase shown to phosphorylate PtpA. Here, we found that PtkA-mediated phosphorylation of PtPA on Tyr-128 and Tyr-129 enhances the PtPA phosphatase activity. Moreover, ex-vivo proteinprotein interaction assays showed that PtpA can be phosphorylated by several eukaryotic-like Ser/ Thr protein kinases, such as protein kinase A (PknA). PknA was found to regulate PtpA phosphatase activity through Thr-45 phosphorylation. These results indicate that members of two independent families of protein kinases tune PtpA activity in Mtb.