CHARACTERIZATION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INTEGRASE MUTANTS EXPRESSED IN ESCHERICHIA-COLI

The eight mutant integrase (IN) proteins of human immunodeficiency vir us type-1 (HIV-1), which have a single point mutation at a highly cons erved central region, were prepared, and characterized in terms of the ir endonucleolytic activities and disintegration activities in vitro. Mutation of two highly conserved amino acids, Asp116 or Glu152, leads to complete loss of both the activities, suggesting that these two ami no acids are directly associated with enzymatic functions. In addition , the mutant of the position Ser147 was found to have highly depressed endonucleolytic activity showing that the reaction was very delayed i n comparison with that of the wild type. However, significant disinteg ration was detected in the mutant Ser147, indicating that the enzymati c mechanisms of the endonucleolytic and disintegration activities are not exactly reverse. The integrase protein with a mutation at the cons erved amino acid Asn117 or Gly118 had a slight loss of the endonucleol ytic activity, while a mutation at the three positions, Tyr143, Ser153 , and Lys159, had no detectable effect on their enzymatic activities. These results indicate that only a few of the conserved amino acids ar e critical for enzymatic activities.