The intracellular pathogen Mycobacterium tuberculosis (Mtb) causes tuberculosis. Enhanced intracellular survival (Eis) protein, secreted by Mtb, enhances survival of Mycobacterium smegmatis (Msm) in macrophages. Mtb Eis was shown to suppress host immune defenses by negatively modulating autophagy, inflammation, and cell death through JNK-dependent inhibition of reactive oxygen species (ROS) generation. Mtb Eis was recently demonstrated to contribute to drug resistance by acetylating multiple amines of aminoglycosides. However, the mechanism of enhanced intracellular survival by Mtb Eis remains unanswered. Therefore, we have characterized both Mtb and Msm Eis proteins biochemically and structurally. We have discovered that Mtb Eis is an efficient N ɛ -acetyltransferase, rapidly acetylating Lys55 of dualspecificity protein phosphatase 16 (DUSP16)/mitogen-activated protein kinase phosphatase-7 (MKP-7), a JNK-specific phosphatase. In contrast, Msm Eis is more efficient as an N α -acetyltransferase. We also show that Msm Eis acetylates aminoglycosides as readily as Mtb Eis. Furthermore, Mtb Eis, but not Msm Eis, inhibits LPSinduced JNK phosphorylation. This functional difference against DUSP16/MKP-7 can be understood by comparing the structures of two Eis proteins. The active site of Mtb Eis with a narrow channel seems more suitable for sequence-specific recognition of the protein substrate than the pocket-shaped active site of Msm Eis. We propose that Mtb Eis initiates the inhibition of JNK-dependent autophagy, phagosome maturation, and ROS generation by acetylating DUSP16/MKP-7. Our work thus provides insight into the mechanism of suppressing host immune responses and enhancing mycobacterial survival within macrophages by Mtb Eis.Rv2416c | lysine acetylation | antituberculosis drug N early one-third of the world's population is infected with Mycobacterium tuberculosis (Mtb). This pathogenic bacterium causes tuberculosis, which claims the lives of millions of people every year (1). Tuberculosis has also become a global health issue owing to the increased incidences of multidrug-resistant and extensively drug-resistant strains of Mtb (2). This makes a search for targets of new antituberculosis drugs urgent. Mtb is a highly successful human pathogen, surviving and multiplying within the human macrophage cells of the infected people (3). Therefore, treatment of tuberculosis is difficult, requiring many months of taking a combination of antibiotics. Mtb has the ability to persist in the form of a long-term asymptomatic infection, referred to as latent tuberculosis (4). Latent tuberculosis becomes activated when the body's immune system is weakened. As a result, tuberculosis is the major cause of death among immuno-compromised AIDS patients (5).In mycobacterial infection, host innate immune responses may play a crucial role in early protection against Mtb infection, leading to establishment of effective adaptive immunity to tuberculosis (6). Additionally, MAPK pathways are activated by Mtb or its components and play an e...

The crystal structure of M. tuberculosis l,d-transpeptidase (LdtMt2; Rv2518c) has been determined in both ligand-free and meropenem-bound forms. The detailed view of the interactions between meropenem and LdtMt2 will be useful in structure-guided discovery of new antituberculosis drugs.

Background: Csd6 is one of the cell shape-determining proteins in H. pylori.Results: The active site of Csd6 is tailored to function as an l,d-carboxypeptidase in the peptidoglycan-trimming process.Conclusion: Csd6 constitutes a new family of l,d-carboxypeptidase.Significance: The substrate limitation of Csd6 is a strategy that H. pylori uses to regulate its helical cell shape and motility.

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