Helicase: This enzyme is responsible for unwinding the DNA double helix, separating the two strands to allow for replication or transcription to occur. By breaking the hydrogen bonds between the base pairs, helicase ensures that the DNA strands are accessible to other enzymes during the process.
Primase: Primase synthesizes a short RNA primer that is necessary for DNA replication to start. This primer provides a free 3’-OH group for DNA polymerases to extend, as they cannot start synthesizing a new strand de novo.
Topoisomerase: This enzyme alleviates the tension that builds up ahead of the helicase as the DNA strands are unwound. By making temporary cuts in the DNA, topoisomerase can relieve supercoiling, allowing replication to proceed smoothly without breaking the DNA strands.
DNA Polymerase III: This is the main enzyme responsible for synthesizing new DNA strands during replication. It adds nucleotides to the growing DNA strand in the 5’ to 3’ direction, using the template strand as a guide. Its high processivity and proofreading ability make it crucial for accurate DNA replication.
DNA Polymerase I: DNA Polymerase I has several functions, including removing the RNA primers laid down by primase and replacing them with DNA nucleotides. It also has proofreading capabilities that help to correct errors in the sequence during replication.
DNA Ligase: This enzyme is essential for joining Okazaki fragments on the lagging strand during DNA replication. After DNA Polymerase I has replaced the RNA primers with DNA, ligase seals the nicks between the fragments, creating a continuous DNA strand.