The PerA helicase

• Helicases are ubiquitous enzymes that unwind the DNA double helix. They use chemical energy from the hydrolysis of NTPs (eg. ATP) and convert it to mechanical energy - they are molecular motors
• Helicases are involved in all aspects of nucleic acid metabolism e.g. DNA replication, repair, transcription, translation, remodelling, packaging
• Classification of helicases is dependent on:

  • Number of conserved signature motifs
  • Directional unwinding
• Signature motif:

  • SF1 and SF2 have 7 motifs encompassing a large number of DNA and RNA helicases from a variety of organisms, unwinding in both directions
  • SF3 has 3 motifs with small viral putative helicases
  • SF4 has 5 motifs and unwind in 5 '- 3 ' direction, and has helicases related to E.coli DnaB - form hexameric assemblies
  • SF5 includes helicases related to Rho (transcription terminator factor) and have sequence similarities to the F0F1 ATPase
• PcrA DNA helicase - bacterial helicase found in gram positive bacteria and are closely related to the gram negative helicases Rep and UvrD, belongs to the SF1 motif
• PcrA DNA helicase activities:

  • Translocation
  • DNA duplex separation
• All the helicase motifs in the PcrA helicase are located in domains 1A and 2A

  Subdomain 1A and 2A contain Tandem RecA fold and core ssDNA motor