Catalyzes the export of L-threonine and L-serine from the cell to the extracellular environment (By similarity). Export is dependent on the proton motive force (By similarity). Required for in vitro growth and survival of bacteria inside macrophages (PubMed:35287590). H(+)(out) + L-threonine(in) = H(+)(in) + L-threonine(out) Expression is significantly increased in clinical isolates (PubMed:35287590). Expression level is positively correlated with lung cavity number of TB patients (PubMed:35287590). Deletion mutant exhibits decreased growth rate compared to wild-type strain in standard culture medium (PubMed:35287590). In addition, the mutant shows decreased survival rate in macrophages (PubMed:35287590). Infected macrophages produce a significantly higher level of TNF-alpha and IL-6 mRNA expression (PubMed:35287590). Belongs to the ThrE exporter (TC 2.A.79) family.