1. The cell cycle-regulated DNA adenine methyltransferase CcrM opens a bubble at its DNA recognition site.
- Author
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Horton JR, Woodcock CB, Opot SB, Reich NO, Zhang X, and Cheng X
- Subjects
- Bacterial Proteins chemistry, Bacterial Proteins genetics, Bacterial Proteins metabolism, Crystallography, X-Ray, DNA chemistry, DNA metabolism, Models, Molecular, Protein Conformation, Protein Domains, Protein Multimerization, Site-Specific DNA-Methyltransferase (Adenine-Specific) genetics, Caulobacter crescentus enzymology, Site-Specific DNA-Methyltransferase (Adenine-Specific) chemistry, Site-Specific DNA-Methyltransferase (Adenine-Specific) metabolism
- Abstract
The Caulobacter crescentus cell cycle-regulated DNA methyltransferase (CcrM) methylates the adenine of hemimethylated GANTC after replication. Here we present the structure of CcrM in complex with double-stranded DNA containing the recognition sequence. CcrM contains an N-terminal methyltransferase domain and a C-terminal nonspecific DNA-binding domain. CcrM is a dimer, with each monomer contacting primarily one DNA strand: the methyltransferase domain of one molecule binds the target strand, recognizes the target sequence, and catalyzes methyl transfer, while the C-terminal domain of the second molecule binds the non-target strand. The DNA contacts at the 5-base pair recognition site results in dramatic DNA distortions including bending, unwinding and base flipping. The two DNA strands are pulled apart, creating a bubble comprising four recognized base pairs. The five bases of the target strand are recognized meticulously by stacking contacts, van der Waals interactions and specific Watson-Crick polar hydrogen bonds to ensure high enzymatic specificity.
- Published
- 2019
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