Sand box 211: Difference between revisions
Celina Pinto (talk | contribs) |
Celina Pinto (talk | contribs) |
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The reaction only takes place if at least two divalent metal ions are bound to the enzyme. However, the DNA binding doesn't need the presence of metal ions. Metal ions participate in the enzymatic catalysis of phosphodiester bond in several ways. For example, they can act as a nucleophile or a general base. They also participate in the catalysis of phosphate diester hydrolysis reactions by interacting with the oxygens which are not involved in the scissile phosphate. | The reaction only takes place if at least two divalent metal ions are bound to the enzyme. However, the DNA binding doesn't need the presence of metal ions. Metal ions participate in the enzymatic catalysis of phosphodiester bond in several ways. For example, they can act as a nucleophile or a general base. They also participate in the catalysis of phosphate diester hydrolysis reactions by interacting with the oxygens which are not involved in the scissile phosphate. | ||
[[Image:mg.jpg]] | [[Image:mg.jpg]] | ||
Following divalent metal ions permit the reaction to take place : Mn2+, Mg2+, Co2+, Zn2+, Fe2+ and Cu2+. However, the reaction is the most efficient with Mn2+ and Mg2+ as cofactors. Furthermore, it has been shown that T5 5' exonuclease is able to cleave double-stranded closed-circular plasmids with an Mn2+ cofactor although this enzyme normally is only able to cleave single-stranded 5' ends. | Following divalent metal ions permit the reaction to take place : Mn2+, Mg2+, Co2+, Zn2+, Fe2+ and Cu2+. However, the reaction is the most efficient with Mn2+ and Mg2+ as cofactors. Furthermore, it has been shown that T5 5' exonuclease is able to cleave double-stranded closed-circular plasmids with an Mn2+ cofactor although this enzyme normally is only able to cleave single-stranded 5' ends. | ||
The two binding sites for metal ions are located near acidic residues ( Asp26, Asp68, Glu128, Asp130, Asp153, Asp155, Asp201 and Asp204) which are responsible for binding them. | The two binding sites for metal ions are located near acidic residues ( Asp26, Asp68, Glu128, Asp130, Asp153, Asp155, Asp201 and Asp204) which are responsible for binding them. | ||