Figure 5. Arginine-to-alanine and hydrophobic variants of SLT-1 A₁ that bind weakly to the monomeric conserved C-terminal motif display altered ribosome-inactivating activities when compared to the wild-type A₁ chain.

Eight ten-fold serial dilutions of the wild-type and each charge and hydrophobic A₁ chain variant was dispensed into an in vitro transcription and translation-coupled rabbit reticulocyte lysate system to monitor their ability to block protein synthesis (methods section). The level of in vitro protein synthesis was assessed by measuring the incorporation of [³⁵S]-methionine into the reporter protein luciferase during its synthesis. The expression of radiolabeled luciferase (arrow) was then resolved by SDS-PAGE and quantified using a phosphorimager. The addition of PBS alone (- lane) was used as a control.