Restriction Endonuclease, Study notes of Plant Biotechnology

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Restriction endonuclease

Presented by : Dr. Ujjwal Layek

Assistant Professor

Department of Botany

Rampurhat College

Nucleic acids

A complex organic substance present in living cells, whose molecules consist of many nucleotides linked in a long chain. E.g.- DNA, RNA

Nuclease Nucleases cleave the phosphodiester bonds of nucleic acids and may be endo or exo, DNases or RNases, topoisomerases, recombinases, ribozymes, or RNA splicing enzymes. Endonuclease Enzymes that cleave the phosphodiester bond within a polynucleotide chain (namely DNA or RNA).

Restriction endonuclease/ restriction enzyme A restriction enzyme is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites

 Type I enzymes (EC 3. 1. 21. 3 ) cleave at sites remote from a recognition site; require both ATP and S-adenosyl-L-methionine to function; multifunctional protein with both restriction digestion and methylase (EC 2. 1. 1. 72 ) activities.  Type II enzymes (EC 3. 1. 21. 4 ) cleave within or at short specific distances from a recognition site; most require magnesium; single function (restriction digestion) enzymes independent of methylase.  Type III enzymes (EC 3. 1. 21. 5 ) cleave at sites a short distance from a recognition site; require ATP (but do not hydrolyse it); S-adenosyl-L- methionine stimulates the reaction but is not required; exist as part of a complex with a modification methylase (EC 2. 1. 1. 72 ).  Type IV enzymes target modified DNA, e.g. methylated, hydroxymethylated and glucosyl-hydroxymethylated DNA  Type V enzymes utilize guide RNAs (gRNAs). Types of restriction enzymes