Table 1.

PPK1 and PPX activities and poly P levels in the WT and mutant

StrainGenotypeEnzyme activity*, units/mg of proteinpoly P, nmol/mg protein
PPK1PPXscPPX1 digestion in vitro
MembraneSolubleMembraneSoluble(−)(+)
PAO1Wild type6,4001859142,28016.70.19
PAOM5Δppk1::Tet152593031,2553.40.03
  • *Strains were grown in LB medium for 6 hr (OD600 = 2.5–2.6); data are the arithmetic means of triplicate assays.

  • Strains were grown in poly P-inducing Mops medium (see Materials and Methods) for 2–3 hr (OD600 = 0.3–0.4); data are the arithmetic means of triplicate assays.

  • Extracted poly P was digested with excess scPPX1 (+) or not (−) to determine its susceptibility to the enzyme.