Bacterial
primase
What enzymes are in the replisome?
The replisome is composed of a number of proteins including
helicase, RFC, PCNA, gyrase/topoisomerase, SSB/RPA, primase, DNA polymerase III, RNAse H, and ligase
.
What does a replisome consist of?
The fundamental components of the replisome are conserved across viruses, bacteria, archaea, and eukaryotes (Table). They include
a helicase to unwind the double-stranded DNA, a polymerase(s) to synthesize new strands of DNA, and a clamp loader to organize the complex on the DNA.
What proteins make up the replisome?
Recent structures of eukaryotic replisome components include the Mcm2-7 com- plex, the CMG helicase, DNA polymerases, a Ctf4 trimer hub and the first look at a core replisome of 20 different proteins containing the helicase,
primase, leading polymerase and a lagging strand polymerase
.
What are the 5 enzymes involved in DNA replication?
The enzymes involved in the replication of prokaryotic DNA are
DNA polymerase I to III, helicase, ligase, primase, sliding clamp, topoisomerase, and single-strand binding proteins (SSBs)
.
What are the 4 steps of replication?
- Step 1: Replication Fork Formation. Before DNA can be replicated, the double stranded molecule must be “unzipped” into two single strands.
- Step 2: Primer Binding. The leading strand is the simplest to replicate.
- Step 3: Elongation.
- Step 4: Termination.
Is Replisome an enzyme?
The replisome is a
large protein complex that carries out DNA replication
, starting at the replication origin. It contains several enzymatic activities, such as helicase, primase and DNA polymerase and creates a replication fork to duplicate both the leading and lagging strand.
Which is the lagging strand?
The lagging strand is
a single DNA strand that, during DNA replication
, is replicated in the 5′ – 3′ direction (opposite direction to the replication fork). DNA is added to the lagging strand in discontinuous chunks called ‘okazaki fragments’.
What is Primase made of?
Archaeal and eukaryote primases are
heterodimeric proteins
with one large regulatory (human PRIM2, p58) and one small catalytic subunit (human PRIM1, p48/p49). The large subunit contains a N-terminal 4Fe–4S cluster, split out in some archaea as PriX/PriCT.
What are Replisomes and Primosomes?
Primosomes are
nucleoproteins assemblies that activate DNA replication forks
. Their primary role is to recruit the replicative helicase onto single-stranded DNA. The “replication restart” primosome, defined in Escherichia coli, is involved in the reactivation of arrested replication forks.
Which helicase in E coli replisome?
DNA replication is carried out by a multiprotein machine called the replisome. In Escherichia coli, the replisome is composed of
the DnaB helicase
, the DnaG primase, the DNA Pol III (αεθ), the processivity factor β clamp (β
2
), the clamp loader (τ
3
δδ′ψχ), and the single strand binding protein SSB (Fig. 1A) (1, 2).
Which protein can catalyze the formation of phosphodiester bonds?
The formation of a phosphodiester bridge is catalyzed by
DNA polymerases
. DNA polymerases catalyze the formation of a phosphodiester bond efficiently only if the base on the incoming nucleoside triphosphate is complementary to the base on the template strand.
What is the replication point?
DNA replication initiates at specific points, called
origins
, where the DNA double helix is unwound. A short segment of RNA, called a primer, is then synthesized and acts as a starting point for new DNA synthesis. An enzyme called DNA polymerase next begins replicating the DNA by matching bases to the original strand.
What are the 3 main enzymes?
- amylase and other carbohydrase enzymes break down starch into sugar.
- protease enzymes break down proteins into amino acids.
- lipase enzymes break down lipids (fats and oils) into fatty acids and glycerol.
Which enzyme is most important in DNA replication?
One of the key molecules in DNA replication is the
enzyme DNA polymerase
. DNA polymerases are responsible for synthesizing DNA: they add nucleotides one by one to the growing DNA chain, incorporating only those that are complementary to the template.
Which enzyme is used in transcription?
Transcription is carried out by an enzyme called
RNA polymerase
and a number of accessory proteins called transcription factors. Transcription factors can bind to specific DNA sequences called enhancer and promoter sequences in order to recruit RNA polymerase to an appropriate transcription site.
