Classification and characteristics ofrestriction endonucleaseBased on the composition, structurecomplexity, cofactor requirements, substratespecificity and cleavage patterns , restrictionendonucleases are classified as three types:Type III *TypeIIITypeXSchool of Life Sciences Tsinghua University
Classification and characteristics of restriction endonuclease Based on the composition, structure complexity, cofactor requirements, substrate specificity and cleavage patterns , restriction endonucleases are classified as three types: Type Ⅰ Type Ⅱ* Type Ⅲ
Type I restriction endonuclease:Recognize specific nucleic acid sequence andincise double strain DNA around this specific site, butthe nucleic acid seguences incised by these enzymesdo not have specificity. The incision is random.Such as EcoB、 EcoK, they are not very useful inDNA recombination and genetic engineering. Theycan not be used to analyse the structure of DNA or toclone genes.文School of Life Sciences Tsinghua University
• Type I restriction endonuclease: Recognize specific nucleic acid sequence and incise double strain DNA around this specific site, but the nucleic acid sequences incised by these enzymes do not have specificity. The incision is random. Such as EcoB、EcoK, they are not very useful in DNA recombination and genetic engineering. They can not be used to analyse the structure of DNA or to clone genes
Type II restriction endonuclease:Recognize specific nucleic acid sequence and incise doublestrain DNA in specific sites in this sequence. With the specificrecognition and incision, type II restriction endonuclease isone of the most widely used enzyme tools in DNArecombination.Generally the nucleic acid sequence recognized by type Irestriction endonuclease contains 4 or 6 nucleosides. Somenucleic acid sequences also contain 5,7,8,9,10,11 nucleosidesThe nucleic acid sequence recognized by type II restrictionendonuclease is a kind of palindrome. There are two patternsof digestion for type II restriction endonuclease:School of Life Sciences Tsinghua University
• TypeⅡ restriction endonuclease: Recognize specific nucleic acid sequence and incise double strain DNA in specific sites in this sequence. With the specific recognition and incision, typeⅡ restriction endonuclease is one of the most widely used enzyme tools in DNA recombination. Generally the nucleic acid sequence recognized by typeⅡ restriction endonuclease contains 4 or 6 nucleosides. Some nucleic acid sequences also contain 5,7,8,9,10,11 nucleosides. The nucleic acid sequence recognized by typeⅡ restriction endonuclease is a kind of palindrome. There are two patterns of digestion for typeⅡ restriction endonuclease:
Cohesive end (Sticky end):For example: nucleic acid sequence recognized by EcoRl:5'...... G'AATT C......3'3'...... C TTIAA'G...... 5After digestionAATTC......35.......GG......5'3'......CTTAASchool of Life Sciences Tsinghua University
Cohesive end (Sticky end): For example: nucleic acid sequence recognized by EcoRI:
Blunt end:For example: nucleic acid sequence recognized by EcoRV5... GAT"ATC...... 3'3'...... CTA'TAG...... 5"AfterdigestionATC...... 3'... GAT5'..3'...... CTATAG......5'XSchool of Life Sciences Tsinghua University
Blunt end: For example: nucleic acid sequence recognized by EcoRV: