Prokaryotic DNA replication - Initiation Flashcards
(14 cards)
Where is replication initiated in prokaryotic cells (E.coli)
Origin of replication (OriC)
How long is the origin of replication?
250 bp
What are the three functional elements of the OriC?
- DnaA-boxes where DnaA protein binds
- A-T rich DNA unwinding elements (DUEs)
- Binding sites of regulatory proteins.
What is a replisome?
Aggregate of DNA replication proteins at the replication fork to form a replication complex.
What is a primosome?
The protein complex that initiates primer synthesis.
What is step 1?
DnaA proteins bind to DnaA boxes in oriC site.
What is step 2?
HU unzips the dsDNA at DUEs
What is step 3?
DnaB protein, with the help of DnaC protein, binds the unwound DNA regions and unwinds the DNA in a bidirectional way creating two replication forks.
What is DnaB?
A helicase
What is DnaC
A helicase loading protein
What is step 4?
SSB protein binds ssDNA to prevent renaturation of two strands and DNA gyrase binds to relieve torsional stress and avoid over-unwinding of DNA.
What type of Topoisomerase is DNA gyrase?
Type II
What is the function of a type I topoisomerase?
Remove negative DNA supercoils or over-unwound DNA by introducing single strand breaks.
What is the function of a type II topoisomerase.
Removes positive DNA supercoils or overwound DNA by cause double stranded breaks.
