Integrase, Lambda-type, N-terminal <p>Phage integrases are enzymes that mediate unidirectional site-specific recombination between two DNA recognition sequences, the phage attachment site, attP, and the bacterial attachment site, attB [<cite idref="PUB00014061"/>]. Integrases may be grouped into two major families, the tyrosine recombinases and the serine recombinases, based on their mode of catalysis. Tyrosine family integrases, such as <taxon tax_id="10710">Bacteriophage lambda</taxon> integrase, utilise a catalytic tyrosine to mediate strand cleavage, tend to recognise longer attP sequences, and require other proteins encoded by the phage or the host bacteria.</p><p>The 356 amino acid lambda integrase consists of two domains: an N-terminal domain (NTD) that includes residues 1 - 64 and is responsible for binding the arm-type sites of attP, and a C-terminal domain that binds the lower affinity core-type sites and contains the catalytic site. The NTD adopts a 4-5 helical bundle fold with two orthogonally packed alpha-hairpins.</p><p>The recombinases Cre from P1 phage, XerD from <taxon tax_id="562">Escherichia coli</taxon>, and Flp from yeast are members of the tyrosine recombinase family, and have a two-domain motif resembling that of lambda integrase, as well as sharing a conserved binding mechanism [<cite idref="PUB00014062"/>, <cite idref="PUB00034645"/>].</p><p>The phage integrase NTD is almost always found with the signature that defines the phage integrase family (see <db_xref db="INTERPRO" dbkey="IPR002104"/>)</p>