Factor that stimulates resuscitation of dormant cells. Has peptidoglycan (PG) hydrolytic activity. Active in the pM concentration range. Has little to no effect on actively-growing cells. PG fragments could either directly activate the resuscitation pathway of dormant bacteria or serve as a substrate for endogenous Rpf, resulting in low molecular weight products with resuscitation activity. Reduces lag phase and enhances the growth of quiescent (1 month-old culture) M.tuberculosis; works best between 8 and 128 pM. Increases the number of bacteria that can be recovered from a 3 month-old culture. Stimulates growth of stationary phase M.bovis (a slowly-growing Mycobacterium) as well as M.smegmatis cells (a fast grower). Binds N,N',N''-triacetylchitotriose (tri-NAG). A fragment (residues 194-362) hydrolyzes an artificial lysozyme substrate 4-methylumbelliferyl-beta-D-N,N',N''-triacetylchitotrioside (MUF tri-NAG). By itself has little activity on cell wall, in combination with RipA is active against cell wall extracts from a number of Actinobacteria; this activity is inhibited by PBP1A (ponA1). Sequential gene disruption indicates RpfB and RpfE are higher than RpfD and RpfC in functional hierarchy. Activity on the artificial substrate MUF tri-NAG is inhibited by 2-nitrophenylthiocyanates (NPT) compounds. The synergistic effects on peptidoglycan degradation of RipA plus RpfB are inhibited by addition of PBP1A (ponA1). Monomer (Probable). Interacts with RipA. Localizes to the septa upon expression in M.smegmatis. Expressed in actively growing cells. An expressed fragment (residues 194-362) hydrolyzes an artificial lysozyme substrate 4-methylumbelliferyl-beta-D-N,N',N''-triacetylchitotrioside (MUF tri-NAG). Not essential, disruption of rpfB alone has no effect on growth or survival in liquid culture, nor in mouse infection models, colonies plated over a 52-week culture period are visibly drier and more friable. Alterations in gene expression are seen. All 5 genes in this family can be deleted without affecting growth in culture, however triple deletion mutants (rpfA-rpfC-rpfB or rpfA-rpfC-rpfD) are not able to resuscitate spontaneously in the presence or absence of O(2), and are attenuated in a mouse infection model. A promising vaccine candidate, an rpfB-encoding DNA vaccine induces elevated cellular immune responses, confers modest but significant protection against intra-tracheal tuberculosis challenge in female C57BL/6 and BALB/c mice. Was identified as a high-confidence drug target. Belongs to the transglycosylase family. Rpf subfamily.