Journal of Biosciences

, Volume 17, Issue 3, pp 217–232 | Cite as

Molecular cloning and sequencing of mcrA locus and identification of McrA protein inEscherichia coli

  • R. Ramalingam
  • Ranjan Prasad
  • R. Shivapriya
  • K. Dharmalingam


The Mcr systems (previously known as Rgl systems) ofEscherichia coli recognize and cleave specific sequences carrying methylated or hydroxymethylated cytosines. We have cloned the mcrA gene and determined its nucleotide sequence. An 831 base pair sequence encodes the McrA protein. Analysis of the sequence data reveals that there arc additional ORFs internal to the above. A phage T7 expression system was used to determine the protein products encoded by the cloned mcrA gene. The results clearly show that a 31 kDa polypeptide is responsible for McrA activity. This is in agreement with the molecular weight deduced from sequence data. McrA protein was found to be localized in the outer membrane ofEscherichia coli. To our knowledge this is the first restriction enzyme localized in the outer membraneof Escherichia coli.


mcrA el4 mcrA sequence T7 expression system 


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Copyright information

© Indian Academy of Sciences 1992

Authors and Affiliations

  • R. Ramalingam
    • 1
  • Ranjan Prasad
    • 1
  • R. Shivapriya
    • 1
  • K. Dharmalingam
    • 1
  1. 1.Genetic Engineering Research Unit, Department of Biotechnology, School of Biological SciencesMadurai Kamaraj UniversityMaduraiIndia

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