PMID:21219463

Citation	Lorenz, C and Büttner, D (2011) Secretion of early and late substrates of the type III secretion system from Xanthomonas is controlled by HpaC and the C-terminal domain of HrcU. Mol. Microbiol. 79:447-67
Abstract	The plant pathogenic bacterium Xanthomonas campestris pv. vesicatoria utilizes a type III secretion (T3S) system to inject effector proteins into eukaryotic cells. T3S substrate specificity is controlled by HpaC, which promotes secretion of translocon and effector proteins but prevents efficient secretion of the early substrate HrpB2. HpaC and HrpB2 interact with the C-terminal domain (HrcU(C) ) of the FlhB/YscU homologue HrcU. Here, we provide experimental evidence that HrcU is proteolytically cleaved at the conserved NPTH motif, which is required for binding of both HpaC and HrpB2 to HrcU(C) . The results of mutant studies showed that cleavage of HrcU contributes to pathogenicity and secretion of late substrates but is dispensable for secretion of HrpB2, which is presumably secreted prior to HrcU cleavage. The introduction of a point mutation (Y318D) into HrcU(C) activated secretion of late substrates in the absence of HpaC and suppressed the hpaC mutant phenotype. However, secretion of HrpB2 was unaffected by HrcU(Y318D) , suggesting that the export of early and late substrates is controlled by independent mechanisms that can be uncoupled. As HrcU(Y318D) did not interact with HrpB2 and HpaC, we propose that the substrate specificity switch leads to the release of HrcU(C) -bound HrpB2 and HpaC.
Links	PubMed PMC3040844 Online version:10.1111/j.1365-2958.2010.07461.x
Keywords	Amino Acid Substitution/genetics; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; Membrane Transport Proteins/genetics; Membrane Transport Proteins/metabolism; Mutagenesis, Site-Directed; Point Mutation; Protein Binding; Protein Interaction Mapping; Protein Transport; Substrate Specificity; Xanthomonas campestris/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
XANC5:Q3BYK6		GO:0009306: protein secretion	ECO:0000315:		P		Figure 3 shows that HrcU does not prevent the expression of secreted proteins, but rather prevents the secretion of these proteins when mutated.	complete CACAO 4648

References

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