In order for HIV to insert it's genetic material into the genome of the infected cell, the enzyme Integrase must help with the integration. It's active site cleaves the DNA with 2 nucleotide overhangs. It is a homodimer.
Integrase cleaves the DNA in such a jagged way 2 nucleotide overhangs are left. The enzyme also leaves sticky ends to the DNA to help it integrate easier into the genome of the host cell. Integrase then takes the genetic material of HIV into the nucleus, and also cleaves the host DNA with 2 nucleotide overhangs as well to integrate the DNA. The HIV genome is still attached to the DNA of the host cell, but is still not implanted in correctly. DNA Ligase comes in to fix the DNA into the host cell genome. The proviral DNA is now ready to undergo transcription and serve as a template for a viral mRNA.
Similarities to enzymes of other organisms
Integrase cleaves the DNA. This gives the enzyme a big similarity to the restriction enzymes used in bacteral recombination. Just like these restriction enzymes, Integrase cuts jagged, and leaves sticky ends. However, restriction enzymes such as EcoR1 leave 5 nucleotide long overhangs, whereas Integrase only leaves 2.
Integrase is made up mostly of alpha helices and some beta sheets in the middle. An interesting fact is that a beta hairpin is located at the top of an enzyme. Beta hairpins are beta sheets that turn over each other.