Biogenesis of Yersinia pestis PsaA in recombinant attenuated Salmonella Typhimurium vaccine (RASV) strain

Authors

  • Ascención Torres-Escobar,

    1. Center for Infectious Diseases and Vaccinology, The Biodesign Institute, School of Life Sciences, Arizona State University, Tempe, AZ, USA
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  • María Dolores Juárez-Rodríguez,

    1. Center for Infectious Diseases and Vaccinology, The Biodesign Institute, School of Life Sciences, Arizona State University, Tempe, AZ, USA
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  • Roy Curtiss III

    1. Center for Infectious Diseases and Vaccinology, The Biodesign Institute, School of Life Sciences, Arizona State University, Tempe, AZ, USA
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  • Editor: Mark Schembri

Correspondence: Roy Curtiss III, Center for Infectious Diseases and Vaccinology, The Biodesign Institute, School of Life Sciences, Arizona State University, PO Box 875401, 1001 S. McAllister Avenue, Tempe, AZ 85287-5401, USA. Tel.: +1 480 727 0445; fax: +1 480 727 0466; e-mail: rcurtiss@asu.edu

Abstract

Yersinia pestis PsaA is an adhesin important for the establishment of bacterial infection. PsaA synthesis requires the products of the psaEFABC genes. Here, by prediction analysis, we identified a PsaA signal sequence with two signal peptidase (SPase) cleavage sites, type-I and type-II (SPase-I and SPase-II). By Edman degradation and site-directed mutagenesis, the precise site for one of these Spase-I PsaA cleavage sites was located between alanine and serine at positions 31 and 32, respectively. Yersinia pestis psaA expression and the role of the PsaB and PsaC proteins were evaluated in recombinant attenuated Salmonella Typhimurium vaccine strains. PsaA was detected in total extracts as a major 15-kDa (mature) and 18-kDa (unprocessed) protein bands. PsaA synthesis was not altered by a ΔA31–ΔS32 double-deletion mutation. In contrast, the synthesis of PsaA (ΔA31–ΔS32) in Y. pestis and delivery to the supernatant was decreased. Otherwise, substitution of the amino acid cysteine at position 26 by valine involved in the SPase-II cleavage site did not show any effect on the secretion of PsaA in Salmonella and Yersinia. These results help clarify the secretion pathway of PsaA for the possible development of vaccines against Y. pestis.

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