May play an important role in host-pathogen interactions and in ESAT-6 secretion. Expression increases during early growth in macrophages (PubMed:16352831). Expression is directly regulated by both the MprAB and TrcRS two-component systems (PubMed:16352831, PubMed:22099420). Negatively regulated by TrcS/TrcR (PubMed:16352831). Activated by MprA/MprB under envelope stress (PubMed:22099420). Expression may also be regulated by sigma E (PubMed:16352831). Deletion of the gene does not affect the synthesis of the major virulence factor ESAT-6, but greatly reduces its secretion. In infected macrophages, Rv1057 deletion significantly reduces the secretion levels of cytokines IL-1 beta, IL-10, TNF-alpha, and INF-gamma, but does not affect IL-4 and IL-8 levels. Deletion of Rv1057 greatly impairs the ability of M.tuberculosis to replicate in macrophages.