FIG. 1.

An aromatic ring is essential for histidine 8 function. (A) Infection of NIH 3T3 cells. Cells were exposed to 10-fold serial dilution of virus stocks, and the virus titer was calculated from the end point dilution (n = 4). Mean results of three independent experiments are shown ± the standard errors. The standard errors for the WT are too small to be seen in the scale of the figure. (B) Incorporation of mutant Envs into virions. Equal volumes of viral pellets were separated on a 8% sodium dodecyl sulfate-polyacrylamide gel and transferred to nitrocellulose membranes. Blots were cut into two parts at 45 kDa. The top part was reacted with anti-SU antisera; the lower part was incubated with anti-CA antisera. (C) Western blot analysis of virus producer cell lysates. The blot was reacted with anti-SU antisera. The numbers at the left of panels B and C indicate the molecular mass in kilodaltons.