TABLE 2.

GTPase activity of RbgA in presence of Na⁺ and K⁺ ions

The intrinsic activity of RbgA was assayed by incubation of 2 μm RbgA with 200 μm GTP for 15 min at 37 °C in the presence of 250 mm NaCl or KCl. Stimulation of GTPase activity by the ribosome was tested by incubation of 100 nm free 50 S subunits with 100 nm RbgA and 200 μm GTP for 15 min at 37 °C in the presence of 250 mm NaCl or KCl. The activity was determined by standard malachite green assay as described under “Experimental Procedures.” S.D. values for three biological replicates are presented.

	Intrinsic GTPase activity	Stimulation of GTPase activity in presence of 50 S subunit
	pmol phosphate/pmol RbgA/min
RbgA + 250 mm KCl	0.26 ± 0.02	13.8 ± 0.85
RbgA + 250 mm NaCl	<0.003	0.78 ± 0.1