This domain is found in Protelomerase from Klebsiella phage phiKO2 (TelK) and similar proteins from tailed bacteriophages and bacterial prophages mainly from Gammaproteobacteria. TelK is a hairpin telomere resolvase with DNA cleavage-rejoining activity that resolves the catenated circular dimer produced from the bidirectional replication of a chromosome. The core of the TelK monomer consists of an N-terminal domain and a catalytic domain connected by a long alpha- helical linker. However, there are two extensions of the protein: a C-terminal DNA binding domain named the stirrup (this entry) and a N-terminal core binding domain. This domain, which shows alpha- helical and beta-hairpin segments, binds to DNA using the winged helix-turn-helix motif and contacts the DNA flanking the cleavage site, extending the DNA binding interface. It is essential for the orientation and extent of DNA bending and for the refolding of cleaved DNA strands into hairpins [1].

1: An interlocked dimer of the protelomerase TelK distorts DNA structure for the formation of hairpin telomeres. Aihara H, Huang WM, Ellenberger T; Mol Cell. 2007;27:901-913. PMID:17889664