Fig. (6) Schematic presentation of mutations introduced in PMTV TGBp1. The protein amino acid sequence is shown as the filled box. The dark grey region indicate the position of the NTPase/helicase sequence domain with the seven conserved motifs I - VI. The box labelled with ‘+’ indicates the positively charged stretch in the N-terminal protein region. Horizontal arrows indicate deletions; the positions of residues at the endpoints of deleted regions are indicated above the arrows. The original sequences and the mutated sequences resulting from point substitutions in mutants GKN, C1 and C2 are shown in boxes.