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Mol Biol (Mosk). 2010 Sep-Oct;44(5):911-21. PubMed

[Secondary structure of SsoII-like (cytosine-5)-DNA methyltransferases N-terminal region determined by circular dichroism spectroscopy].

Riazanova, A. I. u.; Molochkov, N. V.; Abrosimova, L. A.; Alekseevskii, A. V.; Kariagina, A. S.; Protsenko, A. S.; Friedhoff, P.; Oretskaia, T. S.; Kubareva, E. A.

(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.



 


  Московский Государственный Университет имени М.В.Ломоносова



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