Mapping of the antigenic site recognized by antibody Mab 1D5 in Env of the human immunodeficiency virus type 1 by use of a site-directed mutagenesis.
The murine monoclonal antibody (Mab) 1D5 has been reported to block HIV-1 infection by neutralizing a conformation-dependent epitope on the viral surface. To determine the epitope, we have mapped the amino acid residues on the viral surface recognized by this antibody. A total of 33 mutants with substitutions at seven residues located on a three-dimensional model of the gp120-gp41 complex of the envelope glycoprotein (Env) of HIV-1 were tested for 1D5 reactivity. Mutants with the substitutions Phe-33 to Val, Leu-50, Val-51, Asn-88, Phe-89, Lys-90, or Asp-108 failed to react with 1D5. In contrast, mutants with substitutions of Val-32, Lys-33, Gly-41, Leu-42, Asp-43, or Ala-44 reacted with 1D5. A mutation in the complementarity-determining region 2, Asp-43 to Ala, abrogated the binding of 1D5 to the viral envelope. The results demonstrate that the antigenic site recognized by 1D5 is located on the surface of the HIV-1 gp120-gp41 complex, and may be composed of a hydrophobic cluster including Phe-33 and Leu-42. The relative contribution of each of these residues to the binding of 1D5 was then evaluated. In particular, Phe-33 and Leu-42 were found to be critical for the binding of 1D5. Asp-43 and Asn-88 also contributed to the binding of 1D5. In contrast, Lys-33, Gly-41, and Ala-44 were not critical for the binding of 1D5. These results suggest that the 1D5 epitope is localized within the trimeric structure of the envelope glycoprotein of HIV-1.This invention relates to digital-to-analog converters and, in particular, to the conversion of a plurality of digital code values to analog voltage signals.
An electronic apparatus such as, for example, a telephone system, often includes one or more digital-to-analog converters for converting digital signals of a predetermined digital code to
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