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 dual-specificity 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 LPS-induced 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.

We developed a facile method to fabricate highly porous Au-embedded WO₃ nanowire structures for efficient sensing of CH₄ and H₂S gases. Highly porous single-wall carbon nanotubes were used as template to fabricate WO₃ nanowire structures with high porosity. Gold nanoparticles were decorated on the tungsten nanowires by dipping in HAuCl₄ solution, followed by oxidation. The surface morphology, structure and electrical properties of the fabricated WO₃ and Au-embedded WO₃ nanowire structures were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and current–voltage measurements. Formation of a nanowire structure resulted in significant enhancement in sensing response to H₂S and CH₄ gases. Furthermore, Au embedment into the WO₃ nanowire structures remarkably improved the performance of the sensors. The increase in response performance of sensors and adsorption–desorption kinetic processes on the sensing layers were discussed in relation with the role of Au embedment.