Environmental Molecular Sciences Laboratory

A DOE Office of Science User Facility

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CryoEM structural determinations of Bacterial Restriction-Modification systems

Sunday, March 15, 2020
Principal Investigator: 
Betty Shen
Lead Institution: 
Fred Hutchinson Cancer Research Center
Project ID: 

Nuclease enzymes are of enormous importance for a wide range of biological and biotechnology disciplines that require site-specific DNA manipulations. Bacterial R-M systems consist of a restriction endonuclease that specifically cleaves an unmodified nucleotide sequence, and a cognate DNA methyltransferase that protects the host DNA from cleavage. Such enzyme functions provide excellent models for studying specific protein-DNA interactions. Although most of well-understood restriction endonucleases correspond to relatively simple, small enzymes, the majority of such enzymes are instead comprised of large multi-subunit assemblages that coordinate the activity of multiple functional domains: DNA recognition, DNA cleavage, DNA methylation and often DNA translocation. To date, no structures of such large complexes have been determined. We are working towards Cryo-EM structural determinations of two such enzymes: BsaXI which is a large R-M complex that contains three functional subunits in a multi-subunit assemblage and DdrV, which contains the same functions encoded on a single polypeptide