title: Crystal structure of MboIIA methyltransferase.
abstract: DNA methyltransferases (MTases) are sequence-specific enzymes which transfer a methyl group from S-adenosyl-L-methionine (AdoMet) to the amino group of either cytosine or adenine within a recognized DNA sequence. Methylation of a base in a specific DNA sequence protects DNA from nucleolytic cleavage by restriction enzymes recognizing the same DNA sequence. We have determined at 1.74 A resolution the crystal structure of a beta-class DNA MTase MboIIA (M.MboIIA) from the bacterium Moraxella bovis, the smallest DNA MTase determined to date. M.MboIIA methylates the 3' adenine of the pentanucleotide sequence 5'-GAAGA-3'. The protein crystallizes with two molecules in the asymmetric unit which we propose to resemble the dimer when M.MboIIA is not bound to DNA. The overall structure of the enzyme closely resembles that of M.RsrI. However, the cofactor-binding pocket in M.MboIIA forms a closed structure which is in contrast to the open-form structures of other known MTases.
authors.affiliation: Argonne National Laboratory, Biosciences Division and Structural Biology Center, 9700 South Cass Avenue, Argonne, IL 60439, USA.
authors.forename: Jerzy
authors.initials: J
authors.lastname: Osipiuk
authors.forename: Martin A
authors.initials: MA
authors.lastname: Walsh
authors.forename: Andrzej
authors.initials: A
authors.lastname: Joachimiak
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004247:DNA / Q000235:genetics / Q000378:metabolism; D019281:Dimerization; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016955:Moraxella bovis / Q000201:enzymology* / Q000235:genetics; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017386:Sequence Homology, Amino Acid; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific) / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004247:DNA; C047058:DNA modification methylase MboII; D015265:Site-Specific DNA-Methyltransferase (Adenine-Specific)