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 == Publication Abstract from PubMed ==
-Serine integrases catalyze the integration of bacteriophage DNA into a host genome by site-specific recombination between 'attachment sites' in the phage (attP) and the host (attB). The reaction is highly directional; the reverse excision reaction between the product attL and attR sites does not occur in the absence of a phage-encoded factor, nor does recombination occur between other pairings of attachment sites. A mechanistic understanding of how these enzymes achieve site-selectivity and directionality has been limited by a lack of structural models. Here, we report the structure of the C-terminal domains of a serine integrase bound to an attP DNA half-site. The structure leads directly to models for understanding how the integrase-bound attP and attB sites differ, why these enzymes preferentially form attP x attB synaptic complexes to initiate recombination, and how attL x attR recombination is prevented. In these models, different domain organizations on attP vs. attB half-sites allow attachment-site specific interactions to form between integrase subunits via an unusual protruding coiled-coil motif. These interactions are used to preferentially synapse integrase-bound attP and attB and inhibit synapsis of integrase-bound attL and attR. The results provide a structural framework for understanding, testing and engineering serine integrase function.
+Serine integrases are bacteriophage enzymes that carry out site-specific integration and excision of their viral genomes. The integration reaction is highly directional; recombination between the phage attachment site attP and the host attachment site attB to form the hybrid sites attL and attR is essentially irreversible. In a recent model, extended coiled-coil (CC) domains in the integrase subunits are proposed to interact in a way that favors the attPxattB reaction but inhibits the attLxattR reaction. Here, we show for the Listeria innocua integrase (LI Int) system that the CC domain promotes self-interaction in isolated Int and when Int is bound to attachment sites. Three independent crystal structures of the CC domain reveal the molecular nature of the CC dimer interface. Alanine substitutions of key residues in the interface support the functional significance of the structural model and indicate that the same interaction is responsible for promoting integration and for inhibiting excision. An updated model of a LI Int*attL complex that incorporates the high resolution CC dimer structure provides insights that help to explain the unusual CC dimer structure and potential sources of stability in Int*attL and Int*attR complexes. Together, the data provide a molecular basis for understanding serine integrase directionality.
-Attachment site recognition and regulation of directionality by the serine integrases.,Rutherford K, Yuan P, Perry K, Sharp R, Van Duyne GD Nucleic Acids Res. 2013 Sep 1;41(17):8341-56. doi: 10.1093/nar/gkt580. Epub 2013 , Jul 2. PMID:23821671<ref>PMID:23821671</ref>
+Coiled-coil interactions mediate serine integrase directionality.,Gupta K, Sharp R, Yuan JB, Li H, Van Duyne GD Nucleic Acids Res. 2017 Jul 7;45(12):7339-7353. doi: 10.1093/nar/gkx474. PMID:28549184<ref>PMID:28549184</ref>
 From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>