A Switch in the Mechanism of Communication between the Two DNA-Binding Sites in the SfiI Restriction Endonuclease
| Autor: | Susan E. Milsom, Richard B. Sessions, Stephen E. Halford, Stuart R.W. Bellamy, Yana S. Kovacheva |
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| Jazyk: | angličtina |
| Předmět: |
Stereochemistry
Protein Conformation Dimer cooperativity Cooperativity LIN linear SC supercoiled Article chemistry.chemical_compound HEX hexachlorofluorescein Tetramer Structural Biology Mutant protein Protein–DNA interaction Deoxyribonucleases Type II Site-Specific Molecular Biology OC open circle AUC analytical ultracentrifugation Binding Sites allostery KNF Koshland–Nemethy–Filmer MWC Monod–Wyman–Changeux DNA Mr relative molecular mass restriction enzyme DNA binding site Restriction enzyme Kinetics Protein Subunits protein–protein interaction Biochemistry chemistry Amino Acid Substitution DTT dithiothreitol wt wild type DNA–protein interaction Dimerization |
| Zdroj: | Journal of Molecular Biology |
| ISSN: | 0022-2836 |
| DOI: | 10.1016/j.jmb.2007.08.030 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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