TABLE 1.

Summary of mutant envelope glycoproteins and viruses

Envelope glycoproteinCell-cell fusion activityaTm of gp41 six-helix bundle (°C)a,bViral infectivitycgp120 per viriond (arbitrary units)
Wild type+++704,5000.15
L556A±643300.13
L565A±501200.20
V570A±56150.16
Q551A+++742,5000.16
Q563A+++6821,0000.27
  • a The results are from reference 31.

  • b The melting temperature (Tm) of the gp41 six-helix bundle was determined in the N34(L6)C28 model (29).

  • c p24 was determined by antigen capture enzyme-linked immunosorbent assay (Beckman Coulter, Inc.). Nominal viral infectivity (number of foci per nanogram of p24) was calculated by using a dilution of virus that produced 100 foci in a 96-well U87-CD4-CXCR4 cell microculture assay.

  • d The relative amount of gp120 per virion was estimated by Western blot analysis of centrifugally purified virions (51). gp120 was determined with the deglycosylated 55-kDa polypeptide of gp120 (31) and the anti-gp120 MAb Chessie 12 (1). Virion core protein p17 was assessed using immunoglobulin from HIV-infected persons (HIVIG). Antibody binding was visualized by ECL-Plus (Amersham Pharmacia Biotech), and fluorescence was quantitated using a Fuji FLA-3000G analyzer. The ratio of fluorescence intensities is shown.