Excisionase
Encyclopedia
In molecular biology, excisionase is a bacteriophage
protein
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
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 or phosphodiester 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.
Bacteriophage
A bacteriophage is any one of a number of viruses that infect bacteria. They do this by injecting genetic material, which they carry enclosed in an outer protein capsid...
protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
encoded by the Xis gene. It is involved in excisive recombination
Genetic recombination
Genetic recombination is a process by which a molecule of nucleic acid is broken and then joined to a different one. Recombination can occur between similar molecules of DNA, as in homologous recombination, or dissimilar molecules, as in non-homologous end joining. Recombination is a common method...
by regulating the assembly of the excisive intasome and by inhibiting viral
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
integration. It adopts an unusual winged-helix structure
Secondary structure
In biochemistry and structural biology, secondary structure is the general three-dimensional form of local segments of biopolymers such as proteins and nucleic acids...
in which two alpha helices
Alpha helix
A common motif in the secondary structure of proteins, the alpha helix is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier...
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
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
, helix alpha2 is thought to insert into the major groove, while the wing contacts the adjacent minor groove or phosphodiester backbone. The C-terminal region of excisionase is involved in interaction with phage-encoded integrase
Integrase
Retroviral integrase is an enzyme produced by a retrovirus that enables its genetic material to be integrated into the DNA of the infected cell...
(Int), and a putative C-terminal alpha helix
Alpha helix
A common motif in the secondary structure of proteins, the alpha helix is a right-handed coiled or spiral conformation, in which every backbone N-H group donates a hydrogen bond to the backbone C=O group of the amino acid four residues earlier...
may fold
Protein folding
Protein folding is the process by which a protein structure assumes its functional shape or conformation. It is the physical process by which a polypeptide folds into its characteristic and functional three-dimensional structure from random coil....
upon interaction with Int and/or DNA.