DNA Cleavage by the Type IC Restriction-Modification EnzymeEcoR124II

Dreier, Jürg; MacWilliams, Maria P.; Bickle, Thomas A.

doi:10.1006/jmbi.1996.0672

Cited by 42 publications

(40 citation statements)

References 35 publications

(51 reference statements)

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“…For a time it appeared that EcoR124I and -II, members of the IC family, have one rather than two R subunits and that they retain endonuclease activity in the absence of AdoMet (75). However, it has now been shown that the EcoR124I complex has a tendency to lose one HsdR polypeptide (76) and that AdoMet copurifies with EcoR124I and other type IC enzymes (41,133; P. Janscak and T. A. Bickle, personal communication). Type IB complexes readily lose both HsdR subunits (167), but it seems probable that the predominant active complex for any type I R-M system includes two HsdR subunits.…”

Section: Introductionmentioning

confidence: 99%

Type I Restriction Systems: Sophisticated Molecular Machines (a Legacy of Bertani and Weigle)

Murray

2000

Microbiol Mol Biol Rev

406

481

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SUMMARY Restriction enzymes are well known as reagents widely used by molecular biologists for genetic manipulation and analysis, but these reagents represent only one class (type II) of a wider range of enzymes that recognize specific nucleotide sequences in DNA molecules and detect the provenance of the DNA on the basis of specific modifications to their target sequence. Type I restriction and modification (R-M) systems are complex; a single multifunctional enzyme can respond to the modification state of its target sequence with the alternative activities of modification or restriction. In the absence of DNA modification, a type I R-M enzyme behaves like a molecular motor, translocating vast stretches of DNA towards itself before eventually breaking the DNA molecule. These sophisticated enzymes are the focus of this review, which will emphasize those aspects that give insights into more general problems of molecular and microbial biology. Current molecular experiments explore target recognition, intramolecular communication, and enzyme activities, including DNA translocation. Type I R-M systems are notable for their ability to evolve new specificities, even in laboratory cultures. This observation raises the important question of how bacteria protect their chromosomes from destruction by newly acquired restriction specifities. Recent experiments demonstrate proteolytic mechanisms by which cells avoid DNA breakage by a type I R-M system whenever their chromosomal DNA acquires unmodified target sequences. Finally, the review will reflect the present impact of genomic sequences on a field that has previously derived information almost exclusively from the analysis of bacteria commonly studied in the laboratory.

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Section: Introductionmentioning

confidence: 99%

Type I Restriction Systems: Sophisticated Molecular Machines (a Legacy of Bertani and Weigle)

Murray

2000

Microbiol Mol Biol Rev

406

481

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“…Cleavage of the host genome is prevented by the recognition sites being methylated by an associated modification activity in one or both strands 3,4 and by the condensation of the nucleoid. 5 The communication between site-specific recognition and distant non-specific cleavage is by one-dimensional DNA translocation and has been proposed to occur in the following way: 3,4,[6][7][8][9][10][11][12][13][14][15][16] Upon association of an HsdR 2 HsdM 2 HsdS 1 complex (R2) with an unmethylated recognition sequence, the two HsdR subunits begin to hydrolyse ATP. This is coupled to the 1-D motion along DNA of the HsdR subunits, one on each side of the site.…”

Section: Introductionmentioning

confidence: 99%

Continuous Assays for DNA Translocation Using Fluorescent Triplex Dissociation: Application to Type I Restriction Endonucleases

McClelland

Dryden

Szczelkun

2005

Journal of Molecular Biology

108

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“…Three types of DNA restriction systems are presently known: I, II, and III. Because type I restriction enzymes, more precisely restrictionmodification (R-M) systems, recognize a specific sequence but cleave randomly far from the recognition sequence, they are distinguished from type II and III enzymes that recognize and cleave specific target DNA sequences (1,2). The type I enzymes are heterogeneous complexes, consisting of a specificity subunit (S-subunit) that is responsible for recognizing a specific DNA sequence, a methylation subunit (M-subunit) that methylates the target adenine nucleotides recognized by the S-subunit, and a restriction subunit (R-subunit) that randomly cleaves DNA (3,4).…”

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confidence: 99%

Crystal structure of DNA sequence specificity subunit of a type I restriction-modification enzyme and its functional implications

Kim

DeGiovanni

Jancarik

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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Type I restriction-modification enzymes are differentiated from type II and type III enzymes by their recognition of two specific dsDNA sequences separated by a given spacer and cleaving DNA randomly away from the recognition sites. They are oligomeric proteins formed by three subunits: a specificity subunit, a methylation subunit, and a restriction subunit. We solved the crystal structure of a specificity subunit from Methanococcus jannaschii at 2.4-Å resolution. Two highly conserved regions (CRs) in the middle and at the C terminus form a coiled-coil of long antiparallel ␣-helices. Two target recognition domains form globular structures with almost identical topologies and two separate DNA binding clefts with a modeled DNA helix axis positioned across the CR helices. The structure suggests that the coiled-coil CRs act as a molecular ruler for the separation between two recognized DNA sequences. Furthermore, the relative orientation of the two DNA binding clefts suggests kinking of bound dsDNA and exposing of target adenines from the recognized DNA sequences. structural genomics ͉ gi 15669898

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DNA Cleavage by the Type IC Restriction-Modification EnzymeEcoR124II

Cited by 42 publications

References 35 publications

Type I Restriction Systems: Sophisticated Molecular Machines (a Legacy of Bertani and Weigle)

Type I Restriction Systems: Sophisticated Molecular Machines (a Legacy of Bertani and Weigle)

Continuous Assays for DNA Translocation Using Fluorescent Triplex Dissociation: Application to Type I Restriction Endonucleases

Crystal structure of DNA sequence specificity subunit of a type I restriction-modification enzyme and its functional implications

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