Figure 4.

Internalization kinetics of Δ2 vpTR constructs containing point mutations in LL^76–77 or the cluster of acidic amino acids. The internalization rates of the mutant constructs are expressed as percentages of the internalization rate of Δ2 vpTR. The data are the averages ± SEM from at least three independent determinations. The internalization rate of Δ4 vpTR, expressed as a percentage of Δ2 vpTR, is presented as a measure of the nonconcentrative internalization rate. The internalization rates constants for Δ2vpTR-DED^64–66, Δ2vpTR-EED^67–69, and Δ2vpTR-YES^70–72 are different from the internalization rate constant of Δ2vpTR and from the rate for Δ4 vpTR with P values < 0.001 (heteroscedastic, two-tailed Student's t test).