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The structure of Resuscitation Promoting Factor B from M. tuberculosis reveals unexpected ubiquitin-like domains
Structural highlights
FunctionRPFB_MYCTU 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.[1] [2] [3] [4] 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.[5] [6] [7] [8] Publication Abstract from PubMedBACKGROUND: RpfB is a key factor in resuscitation from dormancy of Mycobacterium tuberculosis. This protein is a cell-wall glycosidase, which cleaves cell-wall peptidoglycan. RpfB is structurally complex and is composed of three types of domains, including a catalytic, a G5 and three DUF348 domains. Structural information is currently limited to a portion of the protein including only the catalytic and G5 domains. To gain insights into the structure and function of all domains we have undertaken structural investigations on a large protein fragment containing all three types of domains that constitute RpfB (RpfB3D). METHODS: The structural features of RpfB3D have been investigated combining x-ray crystallography and biophysical studies. RESULTS AND CONCLUSIONS: The crystal structure of RpfB3D provides the first structural characterization of a DUF348 domain and revealed an unexpected structural relationship with ubiquitin. The crystal structure also provides specific structural features of these domains explaining their frequent association with G5 domains. GENERAL SIGNIFICANCE: Results provided novel insights into the mechanism of peptidoglycan degradation necessary to the resuscitation of M. tuberculosis. Features of the DUF348 domain add structural data to a large set of proteins embedding this domain. Based on its structural similarity to ubiquitin and frequent association to the G5 domain, we propose to name this domain as G5-linked-Ubiquitin-like domain, UBLG5. The structure of Resuscitation promoting factor B from M. tuberculosis reveals unexpected ubiquitin-like domains.,Ruggiero A, Squeglia F, Romano M, Vitagliano L, De Simone A, Berisio R Biochim Biophys Acta. 2015 Nov 5. pii: S0304-4165(15)00300-1. doi:, 10.1016/j.bbagen.2015.11.001. PMID:26549874[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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