title: [Secondary structure of SsoII-like (cytosine-5)-DNA methyltransferases N-terminal region determined by circular dichroism spectroscopy].
abstract: (Cytosine-5)-DNA methyltransferase SsoII (M.SsoII) has a long N-terminal region (1-71 residues) preceding the sequence with conservative motifs, which are characteristic for all DNA methyltransferases of such kind. The presence of this region provides M.SsoII capability to act as a transcription regulator in SsoII restriction-modification system. To perform its regulatory function, M.SsoII binds specifically to a 15-mer inverted repeat in the promoter region of SsoII restriction-modification system genes. In the present work, properties of the protein delta(72-379)M.Ecl18kI are studied, which is a deletion mutant of the SsoII-like DNA-methyltransferase M.Ecl18kI and is homologous to M.SsoII N-terminal region. delta(72-379)M.Ecl18kI capability to bind specifically a DNA duplex containing the regulatory site is demonstrated. However, such a binding takes place only in the presence of high protein excess relative to DNA, which could indicate an altered structure in the deletion mutant in comparison with the full-length M.SsoII. Circular dichroism spectroscopy demonstrated that delta(72-379)M.Ecl18kI has a strongly pronounced secondary structure and contains 32% a-helices and 20% beta-sheets. Amino acid sequences alignment of M.SsoII N-terminal region and transcription factors of known spatial structure is made. An assumption is made how alpha-helices and beta-sheets are arranged in M.SsoII N-terminal region.
authors.forename: A Iu
authors.initials: AIu
authors.lastname: Riazanova
authors.forename: N V
authors.initials: NV
authors.lastname: Molochkov
authors.forename: L A
authors.initials: LA
authors.lastname: Abrosimova
authors.forename: A V
authors.initials: AV
authors.lastname: Alekseevskiĭ
authors.forename: A S
authors.initials: AS
authors.lastname: Kariagina
authors.forename: A S
authors.initials: AS
authors.lastname: Protsenko
authors.forename: P
authors.initials: P
authors.lastname: Friedhoff
authors.forename: T S
authors.initials: TS
authors.lastname: Oretskaia
authors.forename: E A
authors.initials: EA
authors.lastname: Kubareva
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D002942:Circular Dichroism / Q000379:methods; D004247:DNA / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry; D015257:DNA-Cytosine Methylases / Q000737:chemistry*; D016972:Enterobacter cloacae / Q000201:enzymology*; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012764:Shigella sonnei / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004247:DNA; C063974:DNA modification methylase SsoII; D015257:DNA-Cytosine Methylases; C114637:Ecl18kI methyltransferase