CHARACTERIZATION OF HIV-1 REVERSE-TRANSCRIPTASE WITH ANTIBODIES INDICATES CONFORMATIONAL DIFFERENCES BETWEEN THE RNASE-H DOMAINS OF P 66 AND P 15

Antibody binding to the p66 and p15 RNaseH regions of HIV-1 reverse transcriptase was compared using a polyclonal rabbit immune serum raised against a synthetic peptide from the RNaseH region of reverse transcriptase (aa 511-527) and six monoclonal antibodies binding to discontinuous epitopes in the RNaseH region of p66. The antigens used in Western blot analysis included recombinantly expressed homodimeric p66 digested with the HIV-1 protease for generation of the p51 and p15 polypeptides and two different length RNaseH domains expressed as TrpE fusion proteins (aa 410-560 and aa 441-560). The polyclonal rabbit antibody binding to a continuous epitope recognized both the TrpE-fusion proteins and also the polypeptides p66 and p15 generated by processing of homodimeric p66 with the viral protease. Two additional cleavage products with estimated molecular weights of 9 and 11 kDa were also detected. The anti-RNaseH MAbs binding to discontinuous epitopes recognized only the RNaseH domain of the p66 polypeptide and the TrpE-RNaseH fusion protein when this was expressed together with the C-terminal part of the polymerase domain. The results indicate conformational differences between the RNaseH domain of the p66 subunit and the RNaseH p15 polypeptide.