Fig. S8.

Enzymatically inactive D82G RelQ does not affect the synthetic activity of WT RelQ. (A) When the D82G (EF2671 locus numbering) mutant is purified following the standard protocol for purification of WT RelQ (19), the resulting protein is contaminated with RNA and exerts a strong inhibitory activity when added in excess over 0.5 μM WT RelQ. (B) Addition of an extra 1 M KCl to buffers used for purification mitigates the RNA contamination. RNA-free D82G RelQ does not inhibit the synthetic activity of 0.5 μM WT RelQ in either the presence or absence of externally added 100 μM ppGpp. Error bars represent SDs of the turnover estimates by linear regression. The experiment was performed twice.