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Characterization of the genetic determinants of SsoII-restriction endonuclease and modification methyltransferase

A S Karyagina1, V G Lunin, I I Nikolskaya

  • 1Institute of Medical Enzymology, U.S.S.R. Academy of Medical Sciences, Moscow.

Gene
|March 1, 1990
PubMed

Insights

Shigella sonnei plasmids P6 and P4 carry genes for SsoI and SsoII restriction enzymes and modification enzymes. The SsoII restriction-modification system was cloned and characterized, revealing its specific DNA cleavage site.

Area of Science:

  • Molecular Biology
  • Genetics
  • Microbiology

Background:

  • Shigella sonnei strain 47 harbors multiple plasmids (P6, P4, P5, P7, P9) encoding various functions.
  • Plasmids P6 and P4 contain genes for SsoI and SsoII restriction endonucleases (ENases) and methyltransferases (MTases).
  • Other identified plasmid functions include colicinogenicity, streptomycin resistance, and DNA transfer.

Purpose of the Study:

  • To clone and characterize the SsoII restriction-modification (R-M) system.
  • To determine the location of SsoII ENase and MTase genes (ssoIIR and ssoIIM) on the P4 plasmid.
  • To define the DNA recognition sequence and cleavage properties of SsoII.

Main Methods:

  • Cloning of SsoII R-M system genes into Escherichia coli.
  • Expression of 35-kDa (ENase) and 43-kDa (MTase) SsoII products.
  • Determination of a restriction map for the P4 plasmid DNA.

Main Results:

  • The SsoII R-M system genes were successfully cloned and expressed in E. coli.
  • The approximate locations of ssoIIR and ssoIIM genes were mapped on the P4 plasmid.
  • SsoII was identified as an isoschizomer of EcoRI, cleaving the 5'-/CCNGG/ sequence and producing 5'-protruding cohesive ends.

Conclusions:

  • The genetic basis and functional characteristics of the SsoII R-M system from Shigella sonnei have been elucidated.
  • The SsoII restriction enzyme exhibits specific DNA cleavage, generating defined cohesive ends.
  • This study provides foundational knowledge for understanding R-M systems in bacterial genetics.

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