A new restriction-modification system, KpnBI, recognized in Klebsiella pneumoniae

A unique DNA restriction-modification (R-M) system has been identified in the GM236 strain of Klebsiella pneumoniae using the newly isolated phage, SBS. The system was designated KpnBI. The gene (hsdRKpnBI) complementing the restriction activity of the KpnBI system was cloned in pBR322. The nucleotide sequence of the cloned DNA revealed one open reading frame (ORF) of 3035 bp. Analysis of the deduced amino-acid sequence shows seven helicase motifs which are common to the restriction (R) subunit of both type-I and type-III R-M systems. Computer analysis (Dendrogram) of the R polypeptide of KpnBI suggests a closer relationship to EcoR124/3I, a member of type-IC family, than to other representative type-I and type-III systems.