Tyrosine recombinase

Tyrosine recombinases of the lambda family also function in eukaryotes. Best known is the FLP (Flip) recombinase, which is encoded by the 2-pm plasmid of Saccharomyces cerevisiae and is thought to function in amplifying the number of plasmid copies.265 The 6.3-kbp plasmid contains a unique DNA sequence that lies between two 599-bp repeats in inverted orientation. Embedded in each repeat is an FLP recombination target (FRT) sequence, which is recognized by the plasmid recombinase. Each FRT segment includes inverted repeats 13 bp in length with an 8-bp spacer between them. As with other integrase systems the... 

Tyrosine recombinases of the lambda family also fimction in eukaryotes. Best known is the FLP (Flip) recombinase, which is encoded by the 2-pm plasmid of Saccharomyces cerevisiae and is thought to fimction in amplifying the number of plasmid copies. The... 

Goodwin TJD, Poulto RTM. A new group of tyrosine recombinase-encoding retrotransposons. Mol Biol Evol. 2004 21 746-59. 

Esposito, D. and Scocca, J. J. (1997) The integrase family of tyrosine recombinases evolution of a conserved active site domain. Nucleic Acids Res 25,3605—3614. 

The intermediates that form in recombination reactions, with their tyrosine adducts possessing 3 -phosphoryl groups, are reminiscent of the intermediates that form in the reactions catalyzed by topoisomerases. This mechanistic similarity reflects deeper evolutionary relationships. Examination of the three-dimensional structures of recombinases and type I topoisomerases reveals that these proteins are related by divergent evolution despite little amino acid sequence similarity (Figure 27,40). From this perspective, the action of a recombinase can be viewed as an intermolecular topoisomerase reaction. In each case, a tyrosine-DNA adduct is formed. In a topoisomerase reaction, this... 

Figure 27.39. Recombination Mechanism. Recombination begins as two DNA molecules come together to form a recombination synapse. One strand from each duplex is cleaved by the recombinase enzyme the 3 end of each of the cleaved strands is linked to a tyrosine (Y) residue on the recombinase enzyme. New phosphodiester bonds are formed when a 5 end of the other cleaved strand in the complex attacks these tyrosine-DNA adducts. After isomerization, these steps are repeated to form the recombined products.

Recombinases cleave DNA strands and form specific adducts in which a tyrosine residue of the enzyme is linked to a 3 -... 

Figure 28.50 Recombinases and topoisomerase i. A superposition of Cre recombinase (blue) and topoisomerase I (orange) reveals that these two enzymes have a common structural core. The positions of the tyrosine residues that participate in DNA cleavage reactions are shown as red spheres for both enzymes. [Drawn from 2CRX.pdb and 1A31.pdb.]...

In contrast to nucleic acid polymerases, polynucleotide processing enzymes often act by mechanisms that involve covalent polynucleotide enzymes as compulsory intermediates (53, 54). The covalent linkages are through phosphodies-ters comprising an enzymic nucleophile, usually the phenolic group of tyrosine, and a nucleotidyl moiety of the nucleic acid. These enzymes are not classified as nucleotidyltransferases, but they catalyze nucleotidyl group transfer as the basic reaction in isomerization processes. Examples are topoisomerases and site-specific recombinases. These enzymes utilize the enzymic nucleophile to cleave the polynucleotide in such a way as to preserve the energy of the covalent bond... 

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