2g1p
From Proteopedia
Structure of E. coli DNA adenine methyltransferase (DAM)
Structural highlights
FunctionDMA_ECOLI Methylates DNA within the sequence GATC and protects the DNA from cleavage by the restriction endonuclease MboI. Although it shares sequence specificity with a number of type II restriction endonucleases and methylases, it is thought to act in postreplication mismatch repair rather than as a part of a restriction modification system. May also play a role in DNA replication. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe structure of the Escherichia coli Dam DNA-(adenine-N6)-methyltransferase in complex with cognate DNA was determined at 1.89 A resolution in the presence of S-adenosyl-L-homocysteine. DNA recognition and the dynamics of base-flipping were studied by site-directed mutagenesis, DNA methylation kinetics and fluorescence stopped-flow experiments. Our data illustrate the mechanism of coupling of DNA recognition and base-flipping. Contacts to the non-target strand in the second (3') half of the GATC site are established by R124 to the fourth base-pair, and by L122 and P134 to the third base-pair. The aromatic ring of Y119 intercalates into the DNA between the second and third base-pairs, which is essential for base-flipping to occur. Compared to previous published structures of bacteriophage T4 Dam, three major new observations are made in E.coli Dam. (1) The first Gua is recognized by K9, removal of which abrogates the first base-pair recognition. (2) The flipped target Ade binds to the surface of EcoDam in the absence of S-adenosyl-L-methionine, which illustrates a possible intermediate in the base-flipping pathway. (3) The orphaned Thy residue displays structural flexibility by adopting an extrahelical or intrahelical position where it is in contact to N120. Structure and substrate recognition of the Escherichia coli DNA adenine methyltransferase.,Horton JR, Liebert K, Bekes M, Jeltsch A, Cheng X J Mol Biol. 2006 Apr 28;358(2):559-70. Epub 2006 Feb 28. PMID:16524590[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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