expressed in BL21(DE3)
and purified by Nickel-affinity chromatography column (GE Healthcare).
DisA was dialyzed into a 10 mM Tris-HCl, pH 8.0, and 100 mM NaCl solution,
and YybT was dialyzed into a 50 mM Tris-HCl, pH 8.0, and 150 mM NaCl
solution. Phosphodiesterase I from Crotalus adamanteus venom (snake venom phosphodiesterase, SVPD) was purchased from Sigma-Aldrich.
For the c-di-AMP synthesis assay, DisA (10 μM) was added to
100 μM ATP in 40 mM Tris-HCl, pH 7.5, 100 mM NaCl, and 10 mM
MgCl2 at 30 °C.7 (link) For the
c-di-AMP cleavage assay, YybT (10 μM) in 100 mM Tris-HCl, pH
8.3, 20 mM KCl, 500 μM MnCl2, and 1 mM DTT17 (link) or SVPD (1 mg/mL) in 50 mM Tris-HCl, pH 8.8,
and 15 mM MgCl2 was used to cleave c-di-AMP (100 μM)
at 37 °C. Reactions were stopped by heating up to 95 °C
for 5 min, and the precipitated proteins were removed by centrifugation.
KBr and coralyne were added to the sample to give final concentrations
of 250 mM and 10 μM for KBr and coralyne, respectively. The
sample was incubated at 4 °C for 12 h.