An inhibitory monoclonal antibody binds at the turn of the helix-turn-helix motif in the N-terminal domain of HIV-1 integrase.
With the increase in our understanding of its structure and enzymatic mechanism, HIV-1 integrase (IN) has become a promising target for designing drugs to treat patients with AIDS. To investigate the structure and function of IN, a panel of monoclonal antibodies (mAbs) directed against HIV-1 IN was raised and characterized previously in this laboratory. Among them, mAbs17, -4, and -33 were found to inhibit IN activity in vitro. In this study, we investigated the interaction of N-terminal-specific mAb17 and its isolated Fab fragment with full-length HIV-1 IN(1-288) and its isolated N-terminal, Zn(2+)-binding domain IN(1-49). Our results show that binding of Zn(2+) to IN(1-49) stabilizes the mAb17-IN complex and that dimer dissociation is not required for binding of the Fab. To identify the epitope recognized by mAb17, we developed a protein footprinting technique based on controlled proteolysis and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Binding was mapped to a region within amino acids Asp(25)-Glu(35). This peptide corresponds to the end of a helix-turn-helix motif in the IN(1-55) NMR structure and contributes to the dimerization of the N-terminal domain. Antibody binding also appears to destabilize the N-terminal helix in this domain. A molecular model of the [IN(1-49)](2).(Fab)(1) complex shows Fab binding across the dimer protein and suggests a potential target for drug design. These data also suggest that mAb17 inhibits integrase activity by blocking critical protein-protein interactions and/or by distorting the orientation of the N-terminal alpha-helix. The relevance of our results to an understanding of IN function is discussed.
Yi
J
J
Fox Chase Cancer Center, Institute for Cancer Research, Philadelphia, Pennsylvania 19111, USA.
Arthur
J W
JW
Dunbrack
R L
RL
Skalka
A M
AM
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000911:Antibodies, Monoclonal / Q000737:chemistry*; D001666:Binding Sites, Antibody; D020134:Catalytic Domain; D004797:Enzyme-Linked Immunosorbent Assay; D019427:HIV Integrase / Q000737:chemistry* / Q000276:immunology*; D015497:HIV-1 / Q000201:enzymology; D019077:Helix-Turn-Helix Motifs; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D000911:Antibodies, Monoclonal; D010446:Peptide Fragments; D011994:Recombinant Proteins; D019427:HIV Integrase