Translocation activity of C-terminal domain of pestivirus Erns and ribotoxin L3 loop

Abstract

The pestivirus envelope glycoprotein Erns has RNase activity and therefore was suspected to enter cells to cleave RNA. The protein contains an RNase domain with a C-terminal extension, which shows homology with a membrane-active peptide. The modular architecture and the C-terminal homology suggested that the C terminus could be responsible for the presumed translocation. Peptides corresponding to the C-terminal domain of Erns and also the homologous L3 loop of ribotoxin II were indeed able to translocate across the eukaryotic cell membrane and were targeted to the nucleoli. The entire Erns protein was also able to translocate into the cell. Furthermore, other labeled proteins and even active enzymes could be transported inside the cell when they were attached to the C-terminal Erns peptide. Translocation was energy-independent and not mediated by a protein receptor. The peptides showed no specificity for cell type or species.