PMID:21576326

Citation	Schulz, S and Büttner, D (2011) Functional characterization of the type III secretion substrate specificity switch protein HpaC from Xanthomonas campestris pv. vesicatoria. Infect. Immun. 79:2998-3011
Abstract	Pathogenicity of Xanthomonas campestris pv. vesicatoria depends on a type III secretion (T3S) system which translocates effector proteins into eukaryotic cells and is associated with an extracellular pilus and a translocon in the host plasma membrane. T3S substrate specificity is controlled by the cytoplasmic switch protein HpaC, which interacts with the C-terminal domain of the inner membrane protein HrcU (HrcU(C)). HpaC promotes the secretion of translocon and effector proteins but prevents the efficient secretion of the early T3S substrate HrpB2, which is required for pilus assembly. In this study, complementation assays with serial 10-amino-acid HpaC deletion derivatives revealed that the T3S substrate specificity switch depends on N- and C-terminal regions of HpaC, whereas amino acids 42 to 101 appear to be dispensable for the contribution of HpaC to the secretion of late substrates. However, deletions in the central region of HpaC affect the secretion of HrpB2, suggesting that the mechanisms underlying HpaC-dependent control of early and late substrates can be uncoupled. The results of interaction and expression studies with HpaC deletion derivatives showed that amino acids 112 to 212 of HpaC provide the binding site for HrcU(C) and severely reduce T3S when expressed ectopically in the wild-type strain. We identified a conserved phenylalanine residue at position 175 of HpaC that is required for both protein function and the binding of HpaC to HrcU(C). Taking these findings together, we concluded that the interaction between HpaC and HrcU(C) is essential but not sufficient for T3S substrate specificity switching.
Links	PubMed PMC3147569 Online version:10.1128/IAI.00180-11
Keywords	Amino Acid Sequence; Bacterial Proteins/genetics; Bacterial Proteins/metabolism; DNA Mutational Analysis; Genetic Complementation Test; Membrane Transport Proteins/genetics; Membrane Transport Proteins/metabolism; Molecular Sequence Data; Mutant Proteins/genetics; Mutant Proteins/metabolism; Protein Binding; Protein Interaction Mapping; Sequence Alignment; Sequence Deletion; Substrate Specificity; Xanthomonas campestris/metabolism
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Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
XANC5:Q3BYK8		GO:0009306: protein secretion	ECO:0000315:		P		Figure 2 shows systematic mutations in the protein sequence that affect virulence via interactions (or lack thereof) with HrcU, a known type III secretion protein	complete CACAO 4317

References

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