Nutrient Transport - Advanced Exercise 2

EnvZ and OmpR proteins play a key role in regulating the transcription of genes encoding outer membrane porins in E. coli.

  1. What type of regulation system do these proteins form, and which type of protein in that system is EnvZ?

  3. What stretch of residues is necessary for ATP binding in EnvZ?

  5. What is the mechanism of autophosophorylation of EnvZ considering that it forms a dimer, and which amino acid is phosphorylated? (Hint: Find the reaction page for the autophosphorylation.)

  7. EnvZ phosphorylates OmpR. What resets this regulatory system, i.e. what converts OmpR back to its unphosphorylated state?  (Hint: refer to the associated Reaction page.)

  9. Under “Sequence Features” for EnvZ, what amino acid at position 347 was mutated? What was it mutated to? How would porin expression be impacted by this mutation?

  11. What mutations in OmpR would give a similar phenotype to that described in your answer to e? Give your answer in terms of general domains rather than specific amino acids.