FIG 11

Substitution of residues located in the TMD and at position 95 in the FL-NA proteins. (A) Enzymatic activity of preparations containing different amounts of FL-NA HN and VN proteins with or without the indicated alteration of the residue at position 95. (B) The specific activity of the FL-NA proteins based on the results shown in panel A relative to the specific activity of the FL-NA HN protein. (C) The relative strength of the HN and VN TMD interactions was determined using the GALLEX system (36). The interaction strengths between the two TMDs were compared in the presence of either 1 (residues 2 to 42) or 8 (residues 2 to 42) juxtamembrane C-terminal amino acids (see Fig. 5 for their sequences). (D) The specific activity of FL-NA HN and VN as well as of their TMD mutants is shown relative to the specific activity of FL-NA HN protein. All graphs show the means from three independent experiments. Error bars indicate standard deviations. Significant differences between the specific activity of the wild-type FL-NA proteins and the mutants thereof (B and D) and the VN and HN TMD interaction strengths (C) were determined using the two-tailed t test (*, P < 0.05; **, P < 0.01; ***, P < 0.001; ****, P < 0.0001).