FIG. 1.

Analysis of NiV-F CT deletion mutants. (A) Schematic of the NiV-F CT deletion mutants. NiV-F CT was divided into four regions (numbered 1, 2, 3, and 4) as described in the text, and the names of the deletion mutants examined are indicated. (B) Western blot analysis of immunoprecipitated surface WT and mutant NiV-F proteins. Briefly, biotinylated cells were lysed, cell surface biotinylated proteins were precipitated with streptavidin agarose beads, and NiV-F was detected in the biotinylated precipitates by Western blotting with either a monoclonal anti-AU1 tag Ab (left part) or a rabbit anti NiV-F₂ antipeptide Ab (3) (right part). Percent processing was calculated as the densitometric units of the F₁ subunit over those of the sum of the precursor F₀ and the F₁ subunits (bottom part) (n = 3). (C) The AU1 tag does not affect cleavage and processing of F. Identical cell surface biotinylation experiments were performed with tagged (F) and untagged versions of WT F (F_NA) and the −T2 mutant (−T2_NA). A rabbit anti NiV-F₂ antipeptide Ab (3) was used to detect NiV-F. (D) Relative levels of CSE and fusion obtained for WT NiV-F and the indicated CT deletion mutants. Fusion was determined by counting nuclei in syncytia per field. At least 10 fields were counted per condition. CSE was determined by flow cytometry with polyclonal anti-NiV-F specific antiserum as described previously (3). Both CSE and fusion levels were separately normalized to levels of WT NiV-F protein, set at 100%. Data shown are averages ± standard errors from three independent experiments.