Cloning and characterization of the genes of the CeqI restriction-modification system

Zsuzsa Izsvák, Zsolt Jobbágy, Imre Takács, Erno Duda

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3 Citations (Scopus)


Two genes from Corynebacterium equii, a Gram-positive bacterium producing the CeqI restriction-modification enzymes were cloned and sequenced. In vivo restriction experiments, DNA and amino acid sequence data suggest that the two genes code for the endonuclease and the methyltransferase enzymes. However, when the two genes are expressed in E. coli, practically no enzyme activity can he detected in the supernatants of sonicated cells. Based on the DNA sequence data CeqI restriction endonuclease (an EcoRV izoschizomer) consists of 270 amino acid residues with a predicted molecular mass of 31.6 kDa, in good agreement with the previously measured 32 ± 2 kDa. The methyltransferase is 517 residues long (approx. 60 kDa). The two genes are in opposite orientation and overlap by 37 base pairs on the chromosome. The deduced amino acid sequence of the putative endonuclease gene revealed long stretches of hydrophobic amino acids, that may form the structural basis of the unusual aggregation properties of the restriction endonuclease. The amino acid sequence of the methylase shows homologies with other type II methyltransferases.

Original languageEnglish
Pages (from-to)895-900
Number of pages6
JournalInternational Journal of Biochemistry and Cell Biology
Issue number6
Publication statusPublished - Jun 1 1997


  • Corynebacterium equii
  • DNA methylation
  • EcoRV izoschizomer
  • Hydrophobicity
  • Primary sequence
  • Recombinant DNA

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology

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