Rv3722c governs aspartate-dependent nitrogen metabolism in Mycobacterium tuberculosis

Organisms are defined by their genomes, yet many distinguishing features of a given organism are encoded by genes that are functionally unannotated. Mycobacterium tuberculosis (Mtb), the leading cause of death due to a single microbe, co-evolved with humans as its only known natural reservoir, yet the factors mediating Mtbs pathogenicity remain incompletely defined. rv3722c is a gene of unknown function predicted to encode a pyridoxal phosphate binding protein and to be essential for in vitro growth of Mtb. Using metabolomic, genetic and structural approaches, we show that Rv3722c is the primary aspartate aminotransferase of Mtb and mediates an essential but underrecognized role in metabolism: nitrogen distribution. Together with the attenuation of Rv3722c-deficient Mtb in macrophages and mice, these results identify aspartate biosynthesis and nitrogen distribution as potential species-selective drug targets in Mtb.