Cantwell, Brian Jay (2006-12). Localization of the phosphatase CheZ to the chemoreceptor patch of Escherichia coli. Doctoral Dissertation. Thesis uri icon

abstract

  • Peritrichously flagellated bacteria carry out chemotaxis by modulating the frequency of switching between smooth swimming and tumbling. The tumbling frequency is controlled by a signal transduction cascade in which transmembrane receptors modulate the activity of a histidine kinase CheA that transfers phosphate to its cognate response regulator CheY. The proteins of the chemotaxis signaling cascade are localized to clusters found primarily at the poles of cells. In this work, the localization of the CheZ protein, a phosphatase that dephosphorylates CheY~P, is examined. Using a CheZ-GFP fusion protein, we show that CheZ was localized to the polar receptor patch via interaction with the short form of CheA (CheAS). Aromatic residues of CheZ near one end of the elongated CheZ four-helix bundle were determined to be critical for localization. Aliphatic residues in CheAS were also determined to be critical for CheZ localization to the receptor patch and substitution of these residues conferred a tumble bias to swimming cells. A mechanism of CheZ localization is proposed in which the CheZ apical loop interacts with a binding site formed by dimerization of the P1 domain of CheAS. The potential role of CheZ localization as a means of coordinating the rotation state of peritrichously distributed flagella is discussed.
  • Peritrichously flagellated bacteria carry out chemotaxis by modulating the frequency
    of switching between smooth swimming and tumbling. The tumbling frequency is
    controlled by a signal transduction cascade in which transmembrane receptors modulate
    the activity of a histidine kinase CheA that transfers phosphate to its cognate response
    regulator CheY. The proteins of the chemotaxis signaling cascade are localized to
    clusters found primarily at the poles of cells. In this work, the localization of the CheZ
    protein, a phosphatase that dephosphorylates CheY~P, is examined. Using a CheZ-GFP
    fusion protein, we show that CheZ was localized to the polar receptor patch via
    interaction with the short form of CheA (CheAS). Aromatic residues of CheZ near one
    end of the elongated CheZ four-helix bundle were determined to be critical for
    localization. Aliphatic residues in CheAS were also determined to be critical for CheZ
    localization to the receptor patch and substitution of these residues conferred a tumble
    bias to swimming cells. A mechanism of CheZ localization is proposed in which the
    CheZ apical loop interacts with a binding site formed by dimerization of the P1 domain
    of CheAS. The potential role of CheZ localization as a means of coordinating the
    rotation state of peritrichously distributed flagella is discussed.

publication date

  • December 2006