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The Secretion Signal of YopN, a Regulatory Protein of the Yersinia enterocolitica Type III Secretion Pathway. John W. Goss, 2004.The type III secretion signal of Yersinia enterocolitica YopN was mapped using a gene fusion approach . yopN codons 1 to 12 were identified as critical for signal function . Several synonymous mutations that abolish secretion of hybrid proteins withoutaltering the codon specificity of yopN mRNA were identified. A Proline-Rich Region with a Highly Periodic Sequence in Streptococcal ß Protein Adopts the Polyproline II Structure and Is Exposed on the Bacterial Surface. Thomas Areschoug, 2002.Proline-rich regions have been identified in many surface proteins of pathogenic streptococci and staphylococci . These regions have been suggested to be located in cell wall-spanning domains and/or to be required for surface expression of the protein . Because little is known about these regions, which are found in extensively studied and biologically important surface proteins, we characterized the proline-rich region in one such protein, the ß protein of group B streptococci . The proline-rich region in ß, designated the XPZ region, has a proline at every third position, and the sequence is highly periodic in other respects . Immunochemical analysis showed that the XPZ region was not associated with the cell wall but was exposed on the bacterial surface . Moreover, characterization of a ß mutant lacking the XPZ region demonstrated that this region was not required for surface expression of the ß protein . Comparison of the XPZ region in different ß proteins showed that it varied in size but always retained the typical sequence periodicity . Circular dichroism spectroscopy indicated that the XPZ region had the structure of a polyproline II helix, an extended and solvent-exposed structure with exactly three residues per turn . Because of the three-residue sequence periodicity in the XPZ region, it is expected to be amphipathic and to have distinct nonpolar and polar surfaces . This study identified a proline-rich structure with unique properties that is exposed on the surface of an important human pathogen .
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