TABLE 1.
Effects of mutations of the codon at position 1555 of the ORF in the full-length clone pOR on NS2-3 cleavage efficiency and stability of the mutations after five passages
| Amino acid (codon) at position 1555a | NS2-3 cleavage efficiency (%)b | Amino acid change at position 1555 after 5 passagesc |
|---|---|---|
| S (TCT) | 88 | None |
| A (GCT) | 82 | None |
| C (TGT) | 78 | None |
| G (GGT) | 76 | None |
| P (CCT) | 72 | None |
| T (ACT) | 70 | None |
| R (CGT) | 61 | None |
| V (GTT) | 48 | A (GCT) |
| F (TTT) | 44 | S (TCT) |
| Y (TAT) | 27 | C (TGT) |
| L (CTT) | 24 | P (CCT) |
| D (GAT) | 18 | G (GGT)/A (GCT) |
| ΔS | 57 | None |
Amino acids at position 1555 of the polyprotein encoded by BVDV Oregon or the different mutants based on pOR. Serine represents the amino acid of the wild-type sequence. In parentheses, the triplets encoding the respective amino acids are indicated, with the exchanged nucleotide(s) underlined.
Efficiency of NS2-3 cleavage determined after transient expression in the T7 vaccina virus system as an average of at least two independent experiments determined as described previously (16).
The analysis of the sequence coding for the amino acid position 1555 after five passages was performed for three independent transfection experiments. For the V, F, Y, and L mutants, the same revertants or pseudorevertans were obtained in each of the three experiments, whereas for the D mutant, alteration to A occurred in two cases and mutation to G occurred in one experiment. In cases in which the introduced mutation was found changed after five passages, the codons are given with the altered nucleotide written in bold type.