Figure 4: ATP binding to HrpR and HrpS subunits.

SDS–PAGE gel of ultraviolet radiated proteins. (a) Co-purified HrpRS in the presence of [α-32P]ATP and when supplemented with excess of non-labelled competitor nucleotides (as indicated). The relative concentrations of the Hrp proteins were visualized using SYPRO Ruby protein staining (Sy), and were compared with the relative intensities of the crosslinked radioactive species (determined by PhosphoImager analysis; IP). Full gel images are shown in Supplementary Figure 5. (b) As in a using PspF1−275 as comparative control, for which specific ATP-binding methodology has been established39,45.