Zinc stimulates Mg2+-dependent 3'-processing activity of human immunodeficiency virus type 1 integrase in vitro

Human immunodeficiency virus type 1 integrase (HIV-1 IN) catalyzes both 3'-donor processing and strand transfer reactions. Previous studies have determined that the N-terminal region, a putative zinc finger, is capable of binding Zn2+. The function of zinc coordination to this domain, however, is still unknown. In this report, we present evidence that Mg2+-dependent 3'-donor processing by HIV-1 IN is enhanced by the addition of Zn2+ in vitro. This activity is inhibited in the presence of the chelator 1,10-phenanthroline (OP). In addition, the Mg2+-dependent 3'-donor processing activity is more sensitive to the concentration of IN than is the Mn2+-dependent activity. A combination of dimethyl sulfoxide (DMSO) and poly(ethylene glycol) (PEG) was found to further activate the Mg2+-dependent 3'-donor processing activity while diminishing the Mn2+-dependent activity. These results suggest factors such as substrate-length, concentration of IN, Zn2+ coordination, and protein-protein interactions are important for efficient and specific donor processing activity with Mg2+ in vitro.