title: Structure of free BglII reveals an unprecedented scissor-like motion for opening an endonuclease.
abstract: Restriction endonuclease BglII completely encircles its target DNA, making contacts to both the major and minor grooves. To allow the DNA to enter and leave the binding cleft, the enzyme dimer has to rearrange. To understand how this occurs, we have solved the structure of the free enzyme at 2.3 A resolution, as a complement to our earlier work on the BglII-DNA complex. Unexpectedly, the enzyme opens by a dramatic 'scissor-like' motion, accompanied by a complete rearrangement of the alpha-helices at the dimer interface. Moreover, within each monomer, a set of residues--a 'lever'--lowers or raises to alternately sequester or expose the active site residues. Such an extreme difference in free versus complexed structures has not been reported for other restriction endonucleases. This elegant mechanism for capturing DNA may extend to other enzymes that encircle DNA.
authors.affiliation: Structural Biology Program, Department of Physiology and Biophysics, Mount Sinai School of Medicine, 1425 Madison Avenue, New York, New York 10029, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Lukacs
authors.forename: R
authors.initials: R
authors.lastname: Kucera
authors.forename: I
authors.initials: I
authors.lastname: Schildkraut
authors.forename: A K
authors.initials: AK
authors.lastname: Aggarwal
mesh_terms: D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific / Q000737:chemistry* / Q000378:metabolism*; D019281:Dimerization; D008958:Models, Molecular; D009038:Motion; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D004247:DNA; C024404:BglII endonuclease; D015252:Deoxyribonucleases, Type II Site-Specific