Integrase - Structure

Structure

All retroviral IN proteins contain three canonical domains, connected by flexible linkers:

  • an N-terminal HH-CC zinc-binding domain (a three-helical bundle stabilised by coordination of a Zn(II) cation)
  • a catalytic core domain (RNaseH fold)
  • a C-terminal DNA-binding domain (SH3 fold)

Crystal and NMR structures of the individual domains and 2-domain constructs of integrases from HIV-1, HIV-2, SIV, and Rous Sarcoma Virus (RSV) have been reported, with the first structures determined in 1994.

Biochemical data and structural data suggest that retroviral IN functions as a tetramer (dimer-of-dimers). All three domains are important for multimerisation and viral DNA binding. Early in 2010, scientists solved the crystal structure of IN from prototype foamy virus (PFV) assembled on viral DNA ends.

In addition, several host cellular proteins have been shown to interact with IN to facilitate the integration process. Human chromatin-associated protein LEDGF, which tightly binds HIV IN and directs HIV PIC towards highly-expressed genes for integration, is an example of such a host factor.

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