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Structure of a two‐domain fragment of HIV‐1 integrase: implications for domain organization in the intact protein

Retroviral integrase, an essential enzyme for replication of human immunodeficiency virus type‐1 (HIV‐1) and other retroviruses, contains three structurally distinct domains, an N‐terminal domain, the catalytic core and a C‐terminal domain. To elucidate their spatial arrangement, we have solved the structure of a fragment of HIV‐1 integrase comprising the N‐terminal and catalytic core domains. This structure reveals a dimer interface between the N‐terminal domains different from that observed for the isolated domain. It also complements the previously determined structure of the C‐terminal two domains of HIV‐1 integrase; superposition of the conserved catalytic core of the two structures results in a plausible full‐length integrase dimer. Furthermore, an integrase tetramer formed by crystal lattice contacts bears structural resemblance to a related bacterial transposase, Tn5, and exhibits positively charged channels suitable for DNA binding.