A List of Proteins Involved in Replication:
In Prokaryotes:
|
Events/Proteins |
Gene |
Mol.wt (KD each) |
Subunits |
Functions |
|
Chain Initiation: |
|
|
|
|
DNA-methylase |
|
32 |
1 |
Methylates A at GATC |
|
Dna-A |
dna-A |
50 |
1 |
Binds to Dna-A boxes |
|
Dna-B |
Dna-B |
50 |
6 |
Helicase, motor protein, moves in 5’>3’ direction |
|
Rep-A? |
|
65-76 |
1 |
Helicase, moves in 3’>5’ direction |
|
Dna-C |
Dna-C |
29 |
1 |
Binds to helicase in 1:1 helps to load |
|
SSB |
ssBs |
19 |
4 |
Binds to p-s-p backbone |
|
Dna-G |
Dna-G |
60 |
1 |
Lays RNA primer on lagging strand |
|
Hup-A/Hup-B |
|
19.5 |
1 each |
Stimulate replication |
|
Top I |
|
100 |
1 |
Single stranded |
|
Gyrase:
|
Top-I Top-II |
97 90 |
2 2 |
Relaxation of super coiled DNA |
|
Elongation:
|
|
|
|
|
DNA pol-I |
|
103 |
1 |
Removal of primers, gap filling, nick translation, DNA repair/recombination |
|
DNA-pol-II |
|
88-90 |
|
DNA-recombination and repair |
|
DNA pol-III (complex) |
Many genes |
>512 |
12, some as dimers |
Replication of leading and lagging strands |
|
Core complex: |
|
|
Dimers, one complex on each strand |
One move on leading strand in 3’>5, on lagging strand moves in 5’>3. Direction |
Alpha |
|
130 |
1 |
5’->3’ polymerase activity |
|
Epsilon |
|
27.5 |
1 |
3’->5’ exonuclease, removes errors |
|
Theta |
|
10 |
1 |
Assists in core assembly |
|
Tau |
|
71 |
1 |
Helps in core dimrization |
|
Gamma-delta complex: |
Many genes |
|
|
Helps in clamp loading on both leading and lagging strands |
Gamma |
|
45.5 |
2 per complex |
Forma complex in ATP dependent manner |
|
Delta |
|
35 |
1 per complex |
|
|
Delta prime |
|
33 |
1 per complex |
|
|
Chi |
|
15 |
1 per complex |
|
|
Psi |
|
12 |
1 per complex |
|
|
Clamps
|
|
|
|
|
|
Beta |
|
40.6 |
2 act as dimer complex |
Holds replicating forks firmly during replication and enhances the processivity of the enzyme |
|
Ligase |
|
74 |
1 |
Ligates nicks or gaps |
|
Termination:
|
|
|
|
|
|
Tus |
|
37.5 |
1 |
Binds to TER sequences and prevent Helicase move into the newly formed DNA helix |
|
Top IV |
Par-C Par-E |
|
|
Catenation and decatanation |
|
Others:
|
|
|
|
|
|
IHF |
Him-A Him-B |
20 |
1+1 |
Integration Host Factor wraps around DNA, binds to Ori-C, required for site specific recombination also |
|
Hu |
|
|
|
Host protein, binds to Ori-C, binding induces DNA bending |
|
Helicase-II |
|
75 |
1 |
Motor protein! |
|
I-protein |
|
22 |
3 |
Involved in primosome formation |
|
N |
|
14 |
2 dimer |
Primosome formation |
|
N’ |
|
14 |
1 |
Primosome formation |
|
N’’ |
|
17 |
1 |
Primosome formation |
|
Fis |
|
|
|
Factor for inversion-stimulation, histone like, bending of DNA |
|
IciA |
|
|
|
Inhibitor of chromosome initiation |
|
IHF |
|
|
|
Integration host factor |
|
Rob |
|
|
|
Origin-Right arm binding protein |
|
Seq A |
|
|
|
Binds and masks A-boxes |
|
|
|
|
|
|
|
|
|
|
|
|
Some Common or Similar Replication Factors among Few Other Systems:
|
Factors |
E.coli |
Hela/SV40 |
T4 phage |
Helicase |
Dna-B |
T-antigen |
P 41 |
|
Loading Helicase/primase |
Dna-C |
T-antigen |
P 59 |
|
Single strand maintenance |
SSB |
RPA |
P 32 |
|
Priming |
Dna-G |
Pol. alpha/primase |
P 61 |
|
Sliding clamp |
Beta subunit |
PCNA |
P 45 (dimer) |
|
Clamp loading |
Gamma/delta complex |
RFC |
44/61 have ATPase activity |
Catalysis |
Pol-III core (alpha/epsilon/theta) |
Pol-delta |
P 43 |
|
Holozyme dimrization |
Tau |
? |
? |
|
RNA removal |
Pol-I |
MF-I |
? |
|
Ligation |
DNA ligase (NAD dependent) |
Ligase-I, ATP dependent |
T4 DNA ligase, ATP dépendent |
|
|
|
|
|