In molecular biology, excisionase is a
bacteriophage protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
encoded by the Xis gene. It is involved in excisive
recombination by regulating the assembly of the excisive intasome and by inhibiting
viral integration. It adopts an unusual winged-helix
structure in which two
alpha helices
The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O group of the amino acid located four residues ear ...
are packed against two extended strands. Also present in the structure is a two-stranded anti-parallel beta-sheet, whose strands are connected by a four-residue wing. During interaction with
DNA, helix alpha2 is thought to insert into the major groove, while the wing contacts the adjacent
minor groove
Minor may refer to:
* Minor (law), a person under the age of certain legal activities.
** A person who has not reached the age of majority
* Academic minor, a secondary field of study in undergraduate education
Music theory
* Minor chord
** Bar ...
or
phosphodiester
In chemistry, a phosphodiester bond occurs when exactly two of the hydroxyl groups () in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. The "bond" involves this linkage . Discussion of phosphodiesters is d ...
backbone. The C-terminal region of excisionase is involved in interaction with phage-encoded
integrase (Int), and a putative C-terminal
alpha helix may
fold upon interaction with Int and/or DNA.
References
{{InterPro content, IPR012884
Protein domains