Fig. 2

The HIV-1 Env TMD allows efficient cell surface localization. a The T-H0 chimera is composed of the extracellular domain of the Tac protein, a 21-hydrophobic residue transmembrane domain (TMD), and a short cytosolic domain (CYT). In T-E14, the Tac extracellular domain is fused to the Env extracellular juxtamembrane segment followed by the Env TMD and its complete cytoplasmic domain. The T-E15 protein exhibits a short truncated cytosolic domain. In T-E26, the Tac extracellular domain is fused directly to the Env TMD and a short cytoplasmic tail. Detailed amino acid sequences are described in Table 1. b Hela cell expressing the indicated Tac chimeric protein were labeled by immunofluorescence before (Surface) and after (Total) permeabilization, using antibodies specific for the Tac extracellular domain. All pictures were taken with the same settings with a confocal microscope (LSM700, Zeiss). Scale bar: 10 μm. c The amount of each Tac chimeric protein present at the cell surface was determined by dividing the surface fluorescence by the total fluorescence. For calibration, this ratio is set to 100 arbitrary units (A.U.) for T-H0. T-E14 is significantly less localized at the cell surface than T-H0 (n = 4; one-way analysis of variance: p < 0.01; *: post-hoc Tukey-Kramer p < 0.05)