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Analysis of type I restriction modification systems in the Neisseriaceae: genetic organization and properties of the gene products
Author(s) -
Piekarowicz Andrzej,
Kłyż Aneta,
Kwiatek Agnieszka,
Stein Daniel C.
Publication year - 2001
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2001.02587.x
Subject(s) - orfs , biology , genetics , gene , locus (genetics) , homology (biology) , sequence analysis , open reading frame , genomic dna , restriction map , sequence alignment , peptide sequence
The hsd locus (host specificity of DNA) was identified in the Neisseria gonorrhoeae genome. The DNA fragment encoding this locus produced an active restriction and modification (R/M) system when cloned into Escherichia coli . This R/M system was designated Ngo AV. The cloned genomic fragment (7800 bp) has the potential to encode seven open reading frames (ORFs). Several of these ORFs had significant homology with other proteins found in the databases: ORF1, the hsdM , a methylase subunit (HsdM); ORF2, a homologue of dinD; ORF3, a homologue of hsdS; ORF4, a homologue of hsdS; and ORF5, an endonuclease subunit hsdR . The endonuclease and methylase subunits possessed strongest protein sequence homology to the Eco R124II R/M system, indicating that Ngo AV belongs to the type IC R/M family. Deletion analysis showed that only ORF3 imparted the sequence specificity of the RM. Ngo AV system, which recognizes an interrupted palindrome sequence (GCAN 8 TGC). The genetic structure of ORF3 (208 amino acids) is almost identical to the structure of the 5′ truncated hsdS genes of Eco DXXI or Eco R124II R/M systems obtained by in vitro manipulation. Genomic sequence analysis allowed us to identify hsd loci with a very high homology to RM. Ngo AV in two strains of Neisseria meningitidis . However, significant differences in the organization and structure of the hsdS genes in both these systems suggests that, if functional, they would possess recognition sites that differ from the gonococcus and from themselves.