FIG. 7.

The SpoT N-terminal half-protein synthesizes (p)ppGpp in vitro. Shown is a PEI-cellulose thin-layer chromatogram of reaction aliquots incubated for 2 h that contained 8 mM ATP, 6 mM [α-³²P]GTP, 15 mM MgCl₂, 1 mM β-mercaptoethanol, 150 mM NaCl, and 50 mM HEPES (pH 8.0). Lane 1, no enzyme control; lanes 2 to 4, SpoT NCH at 2, 4, and 8 μg/ml, respectively; lanes 5 to 7, SpoT NH 1-378 at 3.5, 7, and 14 μg/ml, respectively.