Search results
Results from the WOW.Com Content Network
Specifically, it is the phosphodiester bonds that link the 3' carbon atom of one sugar molecule and the 5' carbon atom of another (hence the name 3', 5' phosphodiester linkage used with reference to this kind of bond in DNA and RNA chains). [3] The involved saccharide groups are deoxyribose in DNA and ribose in RNA.
DNA ligase is a type of enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.It plays a role in repairing single-strand breaks in duplex DNA in living organisms, but some forms (such as DNA ligase IV) may specifically repair double-strand breaks (i.e. a break in both complementary strands of DNA).
Phosphodiester bonds are formed between ribonucleotides by the enzyme RNA polymerase. The RNA chain is synthesized from the 5' end to the 3' end as the 3'-hydroxyl group of the last ribonucleotide in the chain acts as a nucleophile and launches a hydrophilic attack on the 5'-triphosphate of the incoming ribonucleotide, releasing pyrophosphate ...
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.
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 is typically via hydrolysis of a small pendant chemical group on one of the molecules, typically resulting in the formation of new C-O, C-S, or C-N bonds. For example, DNA ligase can join two complementary fragments of nucleic acid by forming phosphodiester bonds, and repair single stranded breaks that arise in double stranded DNA during ...
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 ...
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]