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During adenylylation, there is a nucleophilic attack on the alpha phosphate of ATP from a catalytic lysine resulting in the production of inorganic pyrophosphate (PPi) and a covalently bound lysine-AMP intermediate in the active site of DNA ligase 1. During the AMP transfer step, the DNA ligase becomes associated with the DNA, locates a nick ...
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).
S phase (Synthesis phase) is the phase of the cell cycle in which DNA is replicated, occurring between G 1 phase and G 2 phase. [1] Since accurate duplication of the genome is critical to successful cell division, the processes that occur during S-phase are tightly regulated and widely conserved.
A ubiquitin ligase (also called an E3 ubiquitin ligase) is a protein that recruits an E2 ubiquitin-conjugating enzyme that has been loaded with ubiquitin, recognizes a protein substrate, and assists or directly catalyzes the transfer of ubiquitin from the E2 to the protein substrate. In simple and more general terms, the ligase enables movement ...
Next, biochemical studies revealed that Cdc34 is an E2 enzyme that physically interacts with an E3 ubiquitin ligase complex containing Skp1, Cdc4, and several other proteins. [6] Skp1’s known binding partners—specifically Skp2, Cyclin F, and Cdc4—were found to share an approximately 40 residue motif that was coined the F-box motif.
Skp2 is of considerable interest as a novel and attractive target for cancer therapeutical development, as disrupting the SCF complex will result in increased levels of p27, which will inhibit aberrant cellular proliferation. Although Skp2 is an enzyme, its function requires the assembly of the other members of the SCF complex.
Instead, the pre-RC that is formed during the G 1 of the cell cycle is only activated to unwind the DNA and initiate replication after the cells pass from the G 1 to the S phase of the cell cycle. [2] Once the initiation complex is formed and the cells pass into the S phase, the complex then becomes a replisome.
During G1 phase, the two head-to-head Mcm2-7 rings serve as the scaffold for the assembly of the bidirectional replication initiation complexes at the replication origin. During S phase, the Mcm2-7 complex forms the catalytic core of the Cdc45-MCM-GINS helicase - the DNA unwinding engine of the replisome.