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A Switch in the Mechanism of Communication between the Two DNA-Binding Sites in the SfiI Restriction Endonuclease

While many Type II restriction enzymes are dimers with a single DNA-binding cleft between the subunits, SfiI is a tetramer of identical subunits. Two of its subunits (a dimeric unit) create one DNA-binding cleft, and the other two create a second cleft on the opposite side of the protein. The two cl...

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Autores principales: Bellamy, Stuart R.W., Milsom, Susan E., Kovacheva, Yana S., Sessions, Richard B., Halford, Stephen E.
Formato: Texto
Lenguaje:English
Publicado: Elsevier 2007
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2082129/
https://www.ncbi.nlm.nih.gov/pubmed/17870087
http://dx.doi.org/10.1016/j.jmb.2007.08.030
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author Bellamy, Stuart R.W.
Milsom, Susan E.
Kovacheva, Yana S.
Sessions, Richard B.
Halford, Stephen E.
author_facet Bellamy, Stuart R.W.
Milsom, Susan E.
Kovacheva, Yana S.
Sessions, Richard B.
Halford, Stephen E.
author_sort Bellamy, Stuart R.W.
collection PubMed
description While many Type II restriction enzymes are dimers with a single DNA-binding cleft between the subunits, SfiI is a tetramer of identical subunits. Two of its subunits (a dimeric unit) create one DNA-binding cleft, and the other two create a second cleft on the opposite side of the protein. The two clefts bind specific DNA cooperatively to give a complex of SfiI with two recognition sites. This complex is responsible for essentially all of the DNA-cleavage reactions by SfiI: virtually none is due to the complex with one site. The communication between the DNA-binding clefts was examined by disrupting one of the very few polar interactions in the otherwise hydrophobic interface between the dimeric units: a tyrosine hydroxyl was removed by mutation to phenylalanine. The mutant protein remained tetrameric in solution and could bind two DNA sites. But instead of being activated by binding two sites, like wild-type SfiI, it showed maximal activity when bound to a single site and had a lower activity when bound to two sites. This interaction across the dimer interface thus enforces in wild-type SfiI a cooperative transition between inactive and active states in both dimers, but without this interaction as in the mutant protein, a single dimer can undergo the transition to give a stable intermediate with one inactive dimer and one active dimer.
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spelling pubmed-20821292007-11-28 A Switch in the Mechanism of Communication between the Two DNA-Binding Sites in the SfiI Restriction Endonuclease Bellamy, Stuart R.W. Milsom, Susan E. Kovacheva, Yana S. Sessions, Richard B. Halford, Stephen E. J Mol Biol Article While many Type II restriction enzymes are dimers with a single DNA-binding cleft between the subunits, SfiI is a tetramer of identical subunits. Two of its subunits (a dimeric unit) create one DNA-binding cleft, and the other two create a second cleft on the opposite side of the protein. The two clefts bind specific DNA cooperatively to give a complex of SfiI with two recognition sites. This complex is responsible for essentially all of the DNA-cleavage reactions by SfiI: virtually none is due to the complex with one site. The communication between the DNA-binding clefts was examined by disrupting one of the very few polar interactions in the otherwise hydrophobic interface between the dimeric units: a tyrosine hydroxyl was removed by mutation to phenylalanine. The mutant protein remained tetrameric in solution and could bind two DNA sites. But instead of being activated by binding two sites, like wild-type SfiI, it showed maximal activity when bound to a single site and had a lower activity when bound to two sites. This interaction across the dimer interface thus enforces in wild-type SfiI a cooperative transition between inactive and active states in both dimers, but without this interaction as in the mutant protein, a single dimer can undergo the transition to give a stable intermediate with one inactive dimer and one active dimer. Elsevier 2007-11-09 /pmc/articles/PMC2082129/ /pubmed/17870087 http://dx.doi.org/10.1016/j.jmb.2007.08.030 Text en . https://creativecommons.org/licenses/by/3.0/ Open Access under CC BY 3.0 (https://creativecommons.org/licenses/by/3.0/) license
spellingShingle Article
Bellamy, Stuart R.W.
Milsom, Susan E.
Kovacheva, Yana S.
Sessions, Richard B.
Halford, Stephen E.
A Switch in the Mechanism of Communication between the Two DNA-Binding Sites in the SfiI Restriction Endonuclease
title A Switch in the Mechanism of Communication between the Two DNA-Binding Sites in the SfiI Restriction Endonuclease
title_full A Switch in the Mechanism of Communication between the Two DNA-Binding Sites in the SfiI Restriction Endonuclease
title_fullStr A Switch in the Mechanism of Communication between the Two DNA-Binding Sites in the SfiI Restriction Endonuclease
title_full_unstemmed A Switch in the Mechanism of Communication between the Two DNA-Binding Sites in the SfiI Restriction Endonuclease
title_short A Switch in the Mechanism of Communication between the Two DNA-Binding Sites in the SfiI Restriction Endonuclease
title_sort switch in the mechanism of communication between the two dna-binding sites in the sfii restriction endonuclease
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2082129/
https://www.ncbi.nlm.nih.gov/pubmed/17870087
http://dx.doi.org/10.1016/j.jmb.2007.08.030
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