Phosphorylation assays of L. biflexa Hklep and Rrlep mutant proteins. (A) Site-directed mutagenesis of the L. biflexa histidine kinase protein. The Hklep or Hklep(H98A) proteins were incubated with [γ-32P]ATP for 1 h 30. (B) Site-directed mutagenesis of the L. biflexa response regulator protein. Hklep was incubated with [γ-32P]ATP for 1 h 30 and an equal amount of Rrlep or Rrlep(D53A) proteins was added. The reaction was further incubated for 1 h. Proteins were separated on 12 % SDS-polyacrylamide gel and visualized using autoradiography. The molecular mass is indicated in kDa.