Two domains of superfamily I helicases may exist as separate proteins

Eugene V. Koonin, Kenneth E. Rudd

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


DNA and RNA helicases of superfamily I are characterized by seven conserved motifs. The five N-terminal motifs are separated from the two C- terminal ones by a spacer that is highly variable in both sequence and length, suggesting the existence of two distinct domains. Using computer methods for protein sequence analysis, we show that PhoH, an ATP-binding protein that is conserved in Escherichia coli and Mycobacterium leprae, is homologous to the putative N-terminal domain of the helicases, whereas the putative E. coli protein YjhR is homologous to the C-terminal domain. These findings suggest that the N- and C-terminal domains of superfamily I helicases have distinct activities, with only the N-terminal domain having the ATPase activity. It is speculated that PhoH and YjhR have evolved from helicases through deletion of the portions of the helicase genes coding for the C- and N-terminal domain, respectively.

Original languageEnglish (US)
Pages (from-to)178-180
Number of pages3
JournalProtein Science
Issue number1
StatePublished - Jan 1996


  • ATPases
  • conserved amino acid motifs
  • domain evolution
  • helicases

ASJC Scopus subject areas

  • Biochemistry


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