title: Endonuclease (R) subunits of type-I and type-III restriction-modification enzymes contain a helicase-like domain.
abstract: A statistically significant amino acid sequence similarity is demonstrated between the endonuclease (R) subunit of EcoK restriction-modification (R-M) enzyme, and RNA and DNA helicases of the so-called 'DEAD' family. It is further shown that all three known sequences of R subunits of type-I and type-III R-M enzymes contain the conserved amino acid sequence motifs typical of the previously described helicase superfamily II [(1989) Nucleic Acids Res. 17, 4713-4730]. A hypothesis is proposed that these enzymes may exert helicase activity possibly required for local unwinding of DNA in the cleavage sites.
authors.affiliation: Institute of Poliomyelitis and Viral Encephalitides, USSR Academy of Medical Sciences, Moscow Region.
authors.forename: A E
authors.initials: AE
authors.lastname: Gorbalenya
authors.forename: E V
authors.initials: EV
authors.lastname: Koonin
mesh_terms: D000595:Amino Acid Sequence; D004247:DNA / Q000737:chemistry; D004265:DNA Helicases / Q000235:genetics; D015253:Deoxyribonucleases, Type I Site-Specific / Q000737:chemistry* / Q000235:genetics; D015263:Deoxyribonucleases, Type III Site-Specific / Q000737:chemistry* / Q000235:genetics; D004720:Endonucleases / Q000737:chemistry* / Q000235:genetics; D008969:Molecular Sequence Data; D005810:Multigene Family; D020365:RNA Helicases; D012316:RNA Nucleotidyltransferases / Q000737:chemistry; D016415:Sequence Alignment; D013329:Structure-Activity Relationship
chemical_list: D004247:DNA; D012316:RNA Nucleotidyltransferases; D004720:Endonucleases; C029602:endodeoxyribonuclease EcoK; D015253:Deoxyribonucleases, Type I Site-Specific; D015263:Deoxyribonucleases, Type III Site-Specific; D004265:DNA Helicases; D020365:RNA Helicases