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Identifier

000443485

Title

Structural studies of the M.BseCI methyltransferase from Geobacillus stearothermophilus

Alternative Title

Δομικές μελέτες της M.BseCI μεθυλτρανσφεράσης από το Geobacillus stearothermophilus

Author

Μήτσικας, Δημήτριος Α.

Thesis advisor

Κοκκινίδης, Μιχαήλ

Reviewer

Αθανασάκη, Ειρήνη
Παυλίδης, Ιωάννης

Abstract

DNA modification methyltransferase BseCI (M.BseCI) from Geobacillus stearothermophilus, is an adenine-specific methyltransferase, associated with a restriction endonuclease. It catalyses the methylation of the N6 atom of 3΄ adenine in the sequence 5΄-ATCGAT-3΄ providing, by extent, a defence mechanism against bacterial infection from bacteriophages. Although cytosine-specific methyltransferases have been intensively studied, our knowledge concerning adenine-specific methyltransferases still remains very limited. The work presented here reports the determination of the crystal structure of M.BseCI, both in its apo form (2.5 Å) and in complex with the cofactor product S-adenosyl-L-homocysteine and its cognate DNA sequence in three different methylation states, corresponding to the natural substrate (2.4 Å), the end product of the methylation reaction (2.6 Å), and the unmethylated state (2.3 Å). Like other methyltransferases, the enzyme adopts a bilobed shape and contains the characteristic methylase fold, despite the lack of sequence homology to other enzymes of that family. Surprisingly, extensive structural similarities exist even among DNA target recognition domains of previously determined N6-adenine methyltransferases, suggesting that this group of enzymes might be more uniform than had been expected. The findings reported here, other than merely adding another piece to the puzzle of methyltransferases, provide further insight into the structural basis of adenine-specific methylation and give the opportunity for structural comparisons with various previously determined methyltransferases.

Language

English

Subject

Adomet-dependent Mtases

Base flipping

DNA modification

N6-adenine methylation

Tupe II restriction-modification systems

Απόσπαση βάσης

Μεθυλάσες τύπου ΙΙ

Μεθυλίωση Ν6-αδενίνης

Τροποποίηση DNA