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In DNA replication, for example, formation of the phosphodiester bonds is catalyzed by a DNA polymerase enzyme, using a pair of magnesium cations and other supporting structures. [3] Formation of the bond occurs not only in DNA and RNA replication, but also in the repair and recombination of nucleic acids, and may require the involvement of ...
2) A two-step "associative" (addition-elimination or A N + D N) mechanism that proceeds via a pentavalent phosphorane intermediate. [13] This is represented by the blue dashed lines in the figure at right. 3) A one-step fully synchronous mechanism analogous to S N 2 substitution. Bond formation and breakage occur simultaneously and at the same ...
Phosphodiester (intra-strand) bonds are stronger than hydrogen (inter-strand) bonds. The actual job of the phosphodiester bonds is where in DNA polymers connect the 5' carbon atom of one nucleotide to the 3' carbon atom of another nucleotide, while the hydrogen bonds stabilize DNA double helices across the helix axis but not in the direction of ...
Nick sealing, or phosphodiester bond formation. [5] [6] One particular example of a ligase catalyzing nick closure is the E. coli NAD+ dependent DNA ligase, LigA. LigA is a relevant example as it is structurally similar to a clade of enzymes found across all types of bacteria. [7]
This mechanism, as well as others, allows for cross-regulation of the cAMP and cGMP pathways. PDE12 cleaves 2',5'-phosphodiester bond linking adenosines of the 5'-triphosphorylated oligoadenylates. [ 9 ] [ 10 ] PDE12 is not a member of the cyclic nucleotide phosphodiesterase superfamily that contains PDE1 through PDE11.
The proposed molecular mechanism of cyclic nucleotide specificity of PDEs is the so-called glutamine switch mechanism. In the PDEs that have had their structure solved, there seems to be an invariant glutamine residue that stabilizes the binding of the purine ring in the active site (binding pocket).
The mechanism of the ligation reaction was first elucidated in the laboratory of I. Robert Lehman. [4] [5] Two fragments of DNA may be joined by DNA ligase which catalyzes the formation of a phosphodiester bond between the 3'-hydroxyl group (-OH) at one end of a strand of DNA and the 5'-phosphate group (-PO4) of another.
Thus, a proposed mechanism follows: after a PCNA-DNA polymerase δ complex synthesizes Okazaki fragments, the DNA polymerase δ is released. Then, DNA ligase I binds to the PCNA, which is clamped to the nicks of the lagging strand, and catalyzes the formation of phosphodiester bonds. [12] [13] [14]