HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: mic.0.028944-0v1 155/10/3260    most recent Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Google Scholar Articles by Carter, J. A. Articles by Contreras, I. PubMed PubMed Citation Articles by Carter, J. A. Articles by Contreras, I. Agricola Articles by Carter, J. A. Articles by Contreras, I.

The cellular level of O-antigen polymerase Wzy determines chain length regulation by WzzB and Wzz_pHS-2 in Shigella flexneri 2a

Javier A. Carter^1,

Juan C. Jiménez^1,

¹ Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, PO Box 174 Correo 22, Santiago, Chile
² Infectious Diseases Research Group, Siebens-Drake Research Institute, Department of Microbiology and Immunology, The University of Western Ontario, London, ON N6A 5C1, Canada

The lipopolysaccharide O antigen of Shigella flexneri 2a has two preferred chain lengths, a short (S-OAg) composed of an average of 17 repeated units and a very long (VL-OAg) of about 90 repeated units. These chain length distributions are controlled by the chromosomally encoded WzzB and the plasmid-encoded Wzz_pHS-2 proteins, respectively. In this study, genes wzzB, wzz_pHS-2 and wzy (encoding the O-antigen polymerase) were cloned under the control of arabinose- and rhamnose-inducible promoters to investigate the effect of varying their relative expression levels on O antigen polysaccharide chain length distribution. Controlled expression of the chain length regulators wzzB and wzz_pHS-2 revealed a dose-dependent production of each modal length. Increase in one mode resulted in a parallel decrease in the other, indicating that chain length regulators compete to control the degree of O antigen polymerization. Also, when expression of the wzy gene is low, S-OAg but not VL-OAg is produced. Production of VL-OAg requires high induction levels of wzy. Thus, the level of expression of wzy is critical in determining O antigen modal distribution. Western blot analyses of membrane proteins showed comparable high levels of the WzzB and Wzz_pHS-2 proteins, but very low levels of Wzy. In vivo cross-linking experiments and immunoprecipitation of membrane proteins did not detect any direct interaction between Wzy and WzzB, suggesting the possibility that these two proteins may not interact physically but rather by other means such as via translocated O antigen precursors.

Correspondence
Inés Contreras
icontrer{at}uchile.cl

These authors contributed equally to this work.