FIG. 4.

GTPase activity of the rORF156 protein in the absence or presence of MgCl₂. Activity was measured without MgCl₂ or with 0, 5, and 10 mM MgCl₂ in 50 mM Tris-HEPES (1:1) buffer (pH 8.0) at 37°C at different time intervals by absorbance at 360 nm using the MESG substrate assay system as described in Materials and Methods.