<p>This entry represents the N-terminal domain found in Spo11, a meiotic recombination protein found in eukaryotes, and in subunit A of topoisomerase VI, a type IIB topoisomerase found predominantly in archaea [<cite idref="PUB00007202"/>, <cite idref="PUB00020804"/>]. These two types of proteins share structural homology.</p><p>Spo11 is a meiosis-specific protein that is responsible for the initiation of recombination through the formation of DNA double-strand breaks by a type II DNA topoisomerase-like activity. Spo11 acts in conjunction with several other proteins, including Rec102 in yeast, to bring about meiotic recombination [<cite idref="PUB00020805"/>].</p><p>DNA topoisomerases regulate the number of topological links between two DNA strands (i.e. change the number of superhelical turns) by catalysing transient single- or double-strand breaks, crossing the strands through one another, then resealing the breaks. They can be divided into two classes: type I enzymes (<db_xref db="EC" dbkey="5.99.1.2"/>, topoisomerases I, III and V) break single-strand DNA, and type II enzymes (<db_xref db="EC" dbkey="5.99.1.3"/>, topoisomerases II, IV and VI) break double-strand DNA [<cite idref="PUB00020793"/>]. Topoisomerase VI is a type IIB enzymes that assembles as a heterotetramer, consisting of two A subunits required for DNA cleavage and two B subunits required for ATP hydrolysis. The B subunit is structurally similar to the ATPase domain of type IIA topoisomerases, but the A subunit is distinct, and instead shares homology with the Spo11 protein. </p><p>More information about this protein can be found at Protein of the Month: DNA Topoisomerase [<cite idref="PUB00035961"/>].</p> Spo11/DNA topoisomerase VI, subunit A, N-terminal