1887

Abstract

Type III secretion (T3S) systems play key roles in the assembly of flagella and the translocation of bacterial effector proteins into eukaryotic host cells. Eleven proteins which are conserved among Gram-negative plant and animal pathogenic bacteria have been proposed to build up the basal structure of the T3S system, which spans both inner and outer bacterial membranes. We studied six conserved proteins, termed Hrc, predicted to reside in the inner membrane of the plant pathogen pv. vesicatoria. The membrane topology of HrcD, HrcR, HrcS, HrcT, HrcU and HrcV was studied by translational fusions to a dual alkaline phosphatase–-galactosidase reporter protein. Two proteins, HrcU and HrcV, were found to have the same membrane topology as the homologues YscU and YscV. For HrcR, the membrane topology differed from the model for the homologue from , YscR. For our data on three other protein families, exemplified by HrcD, HrcS and HrcT, we derived the first topology models. Our results provide what is believed to be the first complete model of the inner membrane topology of any bacterial T3S system and will aid in elucidating the architecture of T3S systems by ultrastructural analysis.

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2010-07-01
2019-10-18
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Oligonucleotides used in this study [PDF](74 KB)

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Amino acid sequences of HrcD, HrcR, HrcS, HrcT, HrcU and HrcV, indicating sites of reporter protein fusions and their positions relative to predicted transmembrane segments [PDF](81 KB)

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PhoA activity of HrcR reporter fusions in pv. [PDF](75 KB)

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Multiple sequence alignment of HrcV homologues with predicted transmembrane segments [PDF](105 KB)

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