Lecture on Enzyme Interaction and DNA Replication

Replisome Structure and Function

• Replisome: A complex of multiple enzymes working together for DNA replication.
  • DNA Polymerase 3 subunits: Key components in the replication process.
  • Beta Clamps: Proteins clamping on to ensure processivity during replication.
  • DNA Helicase: Unwinds the DNA double helix.
  • DNA Gyrase: Relieves strain while double-stranded DNA is being unwound.
  • Single-stranded Binding Proteins: Stabilize unwound DNA strands.
• DNA Strands:
  • Lagging Strand: Forms loops to allow replication in a coordinated manner.
  • Leading Strand: Continuously synthesized.

DNA Replication Process

• The replisome pulls the DNA template through, enabling simultaneous replication.
• Lagging Strand Replication:
  • Involves laying down primers, synthesizing DNA, and releasing the new strand.
  • Occurs in fragments known as Okazaki fragments.

Prokaryotic Replication Characteristics

• Bidirectional Replication:
  • Common in prokaryotes with circular chromosomes.
  • Replication forks move in both directions from the origin.
• Origin of Replication (REC):
  • Where replication begins, binding all necessary enzymes.
  • Generates replication forks moving in opposite directions.
  • Enables the rapid replication process, allowing for overlapping replication cycles.
• Theta Structure:
  • Formed by the replication forks moving around the circular chromosome.
  • Named after the Greek letter theta (θ), which it resembles during replication.
• Ter Site:
  • The termination site where replication concludes.
  • Involves complex protein interactions to complete replication.

Fast Replication in Bacteria and Archaea

• Ability to initiate new rounds of replication even before the previous round has concluded.
• Results in rapid DNA replication, aiding fast bacterial and archaeal proliferation.

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• Videos and further exploration on the replisome and DNA replication process to be provided in class.