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