In: Biology
Which protein does NOT contribute in some fashion to the low rate of errors in DNA replication in E. coli?
a.DNA Pol III
b. DnaG
c.MutS
d. Dam methylase
e. UvrD
Answer. DnaG
DNA pol II is the main replicating polymerase in prokaryotes. It associates with clamp proteins and assembless into a holoenzyme with a high processivity. It possesses a 5'-->3', 3'-->5' exonuclease activity and a 3'-->5' polymerase activity.3'-->5' exonuclease activity is called the proofreading activity.
DnaG serves as aprimase. It synthesizes the primer (short stretch of RNA) required for replication. DNA polymerase can extend an existing stretch of nucleotides but however cannot start synthesis de novo. RNA polymerase is different in this sense as it can start synthesis de novo.
MutS protein is involved in the mismatch repair pathway.
Dam methylase is a methyl methylates the adenine residue present in the sequence 5'-GATC-3'. It helps the enzymes of the mismatch repair pathway to distinguish between the parent and daughter strand. Parent strands are methylated while daughter strands are not.
UvrD is a helicase which takes part in nucleotide excission repair pathway.
Thus, only DnaG does not contribute to the low error rate during replication.