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  • 1.
    Amer, Ayad
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Costa, Tiago
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Gurung,, Jyoti
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Avican, Ummehan
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Forsberg, Åke
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Francis, Matthew
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Functional consequences of site-directed mutagenesis in theC-terminus of YopN, a Yersinia pseudotuberculosis regulator ofYop secretionManuscript (preprint) (Other academic)
    Abstract [en]

    Pathogenic Yersinia spp. utilizes the Ysc-Yop type III secretion system to targetYop effector proteins into the cytosol of host immune cells. Internalizedeffectors alter specific signaling pathways to neutralize immune cell-dependentphagocytosis, killing and pro-inflammatory responsiveness. This enablesextracellular bacterial multiplication and survival in immune tissue. Central tothe temporal control of Yop type III secretion is the regulator YopN. Incomplex with TyeA, YopN acts to plug the inner face of the type III secretionchannel, denying entry to other Yop substrates until after YopN has beensecreted. A +1 frameshift event in the 3-prime end of yopN results in thesynthesis of a singular secreted YopN-TyeA polypeptide chimera that retainssome regulatory function. As the C-terminal coding sequence of YopN in thishybrid product differs greatly from native sequence, we used site-directedmutagenesis to determine the functional significance of this segment. YopNtruncated at residue 287 or containing a shuffled sequence covering 288 to 293retains full function both in vitro and in vivo. Thus, the extreme C-terminus isapparently superfluous to YopN function. In contrast, a YopN varianttruncated after residue 278 was completely unstable, and these bacteria hadlost all control of T3S activity, and failed to defend against immune cell killing.Interestingly, inclusion of a shuffled sequence from residues 279 to 287recovered some T3S control over function. Hence, the YopN segmentencompassing 279 to 287 is essential for full function, although the exact aminoacid sequence is less important.

  • 2.
    Amer, Ayad
    et al.
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Gurung, Jyoti
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Francis, Matthew
    Umeå University, Faculty of Science and Technology, Department of Molecular Biology (Faculty of Science and Technology).
    Yersinia pseudotuberculosis type III secretion is reliant upon anauthentic N‐terminal YscX secretor domainManuscript (preprint) (Other academic)
    Abstract [en]

    Certain Gram‐negative bacteria use type III secretion systems to deliver effectorproteins into eukaryotic cells, serving either parasitic or mutualistic roles inside the hostcell. About 25 structural proteins are needed to assemble and deliver effector proteins.Collections of these proteins are quite well characterized, although the function ofsome continues to remain obscure. This is true for the Yersinia Ysc‐Yop systemcomponents YscX, a secreted substrate and YscY, its cognate non‐secreted chaperone.Despite recent evidence suggesting that they might coordinate Yop substrate secretion,YscX and YscY remain poorly characterized. To further investigate the function of theseproteins in the enteropathogen Y. pseudotuberculosis, we explored correlationsbetween the YscX N‐terminal segment, YscX secretion, as well as the secretion of otherYops. Analysis of a series of chimeric substrates in which the extreme YscX N‐terminushad been exchanged with equivalent functional secretion signals of other Ysc‐Yopsubstrates revealed that this segment contains non‐redundant information needed forYscX function, which includes permitting surface polymerization of the YscF needle andYops secretion. Further, in cis deletion of the YscX N‐terminus and ectopic expression ofepitope tagged YscX variants again correlated stable YscX production but not secretionto the type III secretion of Yops. Despite this, the first 5 codons were determined toconstitute a minimal signal capable of promoting secretion of the signalless ‐lactamasereporter. Hence, YscX does contain a fully equipped N‐terminal secretor domain topromote secretion of self. Nevertheless, the primary role of this N‐terminal segmentmust be to assemble an operational secretion system, and this occurs independently ofYscX secretion.

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