FIGURE 4.

The activity of PVND motif variants in the RF1 recognition loop. (Top) The RF1 PVND variants with shortened loop size as for C. elegans (A) or as for a typical RF (B). Amino acid substitutions are shown in black. (Middle) The codon-dependent peptidyl-tRNA hydrolysis activities of the RF1 PVND motif variants at the standard stop codons UAG, UAA, and UGA. The release activities are expressed as percentages of the release activity of RF1 for UAG and UAA, and RF2 for UGA. The RF variants were assayed and data analyzed as for Figure 1C. (Bottom) The effect of overexpression of the RF1 PVND variants on termination efficiency at the Ra UAG Ra termination context in the E. coli suppressor strain XA102. Replicates and analyses were as for Figure 3D.