Motors, switches, and contacts in the replisome

Samir M. Hamdan, Charles C. Richardson

Research output: Contribution to journalReview articlepeer-review

140 Scopus citations


Replisomes are the protein assemblies that replicate DNA. They function as molecular motors to catalyze template-mediated polymerization of nucleotides, unwinding of DNA, the synthesis of RNA primers, and the assembly of proteins on DNA. The replisome of bacteriophage T7 contains a minimum of proteins, thus facilitating its study. This review describes the molecular motors and coordination of their activities, with emphasis on the T7 replisome. Nucleotide selection, movement of the polymerase, binding of the processivity factor, unwinding of DNA, and RNA primer synthesis all require conformational changes and protein contacts. Lagging-strand synthesis is mediated via a replication loop whose formation and resolution is dictated by switches to yield Okazaki fragments of discrete size. Both strands are synthesized at identical rates, controlled by a molecular brake that halts leading-strand synthesis during primer synthesis. The helicase serves as a reservoir for polymerases that can initiate DNA synthesis at the replication fork. We comment on the differences in other systems where applicable.

Original languageEnglish (US)
Pages (from-to)205-243
Number of pages39
JournalAnnual Review of Biochemistry
StatePublished - 2009


  • DNA
  • Helicase
  • Okazaki fragments
  • Polymerase
  • Primase
  • Processivity
  • Replication
  • Replication fork

ASJC Scopus subject areas

  • Biochemistry


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