Lai, Runzhi (2007-05). Signal processing within and between bacterial chemoreceptors. Doctoral Dissertation. Thesis uri icon

abstract

  • The key control step in E. coli chemotaxis is regulation of CheA kinase activity by a set of four transmembrane chemoreceptors. The receptor dimers can form trimeric complexes (trimers of dimers), and these trimers can be joined by a bridge thought to consist of a CheW monomer, a CheA dimer, and a second CheW monomer. It has been proposed that trimers of receptor dimers may be joined by CheW-CheA dimer-CheW links to form an extended hexagonal lattice that may be the structural basis of the chemoreceptor patches seen in E. coli. The receptor/CheA/CheW ternary complex is a membrane-spanning allosteric enzyme whose activity is regulated by protein interactions. The study presented in this dissertation investigated intermolecular and intramolecular interactions that affect the chemotactic signal processing. I have examined functional interactions between the serine receptor Tsr and the aspartate receptor Tar using a receptor coupled in vitro phosphorylation assay. The results reveal the emergent properties of mixed receptor populations and emphasize their importance in the integrated signal processing that underlies bacterial chemotaxis. A mutational analysis of the extreme C-terminus (last fifty residues) of Tar is also presented. The results implicate the receptor C-terminus in maintenance of baseline receptor activity and in attractant-induced transmembrane signaling. They also suggest how adaptive methylation might counteract the effects of attractant binding.
  • The key control step in E. coli chemotaxis is regulation of CheA kinase activity by
    a set of four transmembrane chemoreceptors. The receptor dimers can form trimeric
    complexes (trimers of dimers), and these trimers can be joined by a bridge thought to
    consist of a CheW monomer, a CheA dimer, and a second CheW monomer. It has been
    proposed that trimers of receptor dimers may be joined by CheW-CheA dimer-CheW
    links to form an extended hexagonal lattice that may be the structural basis of the
    chemoreceptor patches seen in E. coli. The receptor/CheA/CheW ternary complex is a
    membrane-spanning allosteric enzyme whose activity is regulated by protein
    interactions. The study presented in this dissertation investigated intermolecular and
    intramolecular interactions that affect the chemotactic signal processing. I have
    examined functional interactions between the serine receptor Tsr and the aspartate
    receptor Tar using a receptor coupled in vitro phosphorylation assay.
    The results reveal the emergent properties of mixed receptor populations and
    emphasize their importance in the integrated signal processing that underlies bacterial
    chemotaxis. A mutational analysis of the extreme C-terminus (last fifty residues) of Tar
    is also presented. The results implicate the receptor C-terminus in maintenance of baseline receptor activity and in attractant-induced transmembrane signaling. They also
    suggest how adaptive methylation might counteract the effects of attractant binding.

publication date

  • May 2007