J Infect Dis 2019 Apr 18. Epub 2019 Apr 18.
Department of Microbiology, Immunology, and Biochemistry, University of Tennessee Health Science Center, Memphis, TN.
Mycobacterium tuberculosis (Mtb) lipid metabolism pathways facilitate access to carbon and energy sources for Mtb during infection. A Mtb gene, Rv1075c, was annotated as a conserved hypothetical protein. We have identified that Rv1075c amino acid sequence shares similarities to other bacterial lipase/esterases. With the overexpressed and purified rRv1075c protein, we demonstrated that it had an esterase activity, and preferred short-chain fatty acids, with the highest activity on acetate. Its activity was the highest at 45 °C and pH=9. Site-direct mutagenesis revealed its activity triad as Ser80, Asp244, and His247. We further determined that rRv1075c hydrolyzed triacetin and tributyrin, and the Rv1075c protein was mainly distributed in cell wall and cell membrane of Mtb. Its transcriptional expression was induced at pH=4.5, a condition mimicking the acidic phagosome of macrophage. The mutation of Rv1075c led to significantly reduced bacterial growth in THP-1 cells and human peripheral blood mononuclear derived macrophages, and attenuated Mtb infection in mice (with ~7-fold bacterial load reduction in mouse lungs). Our data suggest that Rv1075c is likely involved in ester and fatty acid metabolism to help Mtb utilize carbon and energy while Mtb stays inside of host cells.