FIG 2.

Effects of PB1 amino acid substitutions on polymerase activity. (A and B) The effects of 7 amino acid substitutions in WB PB1 on polymerase activity were analyzed in a WB background (A) and in an LP background (B). Asterisks indicate significant differences (P < 0.01) from WB (A) and from LP(W/PB1) (B). (C) Three amino acid substitutions in LP PB1 were analyzed for their effects on polymerase activity in WB and LP. Asterisks indicate significant differences among WB(L/PB1) variants in the WB background or among LP variants in the LP background (P < 0.01). Values are means ± standard deviations for three or more independent experiments. Statistical differences in mean polymerase activities were assessed with Bonferroni's multiple-comparison test.