Figure 4.

(A) K⁺ is an essential co-activator of rN-TcsL. rN-TcsL (100 nM) was incubated with 100 µM·UDP-[¹⁴C]glucose in the presence of 1 mM·Mn²⁺ and increasing concentrations of K⁺ and Na⁺ as indicated at 37 °C for 30 min. (B) Divalent metal ion activation of rN-TcdB. UDP-[¹⁴C]glucose (100 µM) was incubated in the presence of rN-TcdB (100 nM) with the indicated divalent metal ions (1 mM) at 37 °C for 30 min. UDP-[¹⁴C]glucose and [¹⁴C]glucose were separated by thin layer chromatography on PEI cellulose and visualized by autoradiography. Signal intensities of formed [¹⁴C]glucose were quantified and are given as means ± SD (n = 3).