Isocaudomer
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Isocaudomers are pairs of
restriction enzyme A restriction enzyme, restriction endonuclease, REase, ENase or'' restrictase '' is an enzyme that cleaves DNA into fragments at or near specific recognition sites within molecules known as restriction sites. Restriction enzymes are one class o ...
s that have slightly different
recognition sequence A recognition sequence is a DNA sequence to which a structural motif of a DNA-binding domain exhibits binding specificity. Recognition sequences are palindromes. The transcription factor Sp1 for example, binds the sequences 5'-(G/T)GGGCGG(G/A)( ...
s, but upon cleavage of DNA, generate identical overhanging termini sequences. These sequences can be ligated to one another, but then form an asymmetrical sequence that cannot be cleaved by a restriction enzyme.


Examples

For example the enzymes Mbo I and BamH I are isocaudomers: Mbo I N*GATC N N CTAG*N BamH I G*GATC C C CTAG*G N represents any of the four
nucleotide Nucleotides are Organic compound, organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both o ...
s. Independently of which nucleotide is present when cleaving with MboI, after cleavage with either enzyme, all termini have the central tetranucleotide - GATC. This allows fragments generated with one enzyme to anneal with fragments generated with the other enzyme. This can be used for elimination of
restriction site In molecular biology, restriction sites, or restriction recognition sites, are regions of a DNA molecule containing specific (4-8 base pairs in length) sequences of nucleotides; these are recognized by restriction enzymes, which cleave the DNA at ...
s from the resulting DNA fragment. For example: Not I ''GC*GGCC GC'' ''CG CCGG*CG'' Bsp120 I G*GGCC C C CCGG*G In the above example, both enzymes produce tetranucleotides CCGG which can anneal to one another. However, resulting DNA sequence will be: ''GC''GGCCC ''CGCCGG''G where the nucleotides shown in italic originate from NotI-cut site, and those in bold from Bsp120I-cut one. Note that the resulting sequence is not recognised by either of the two enzymes. Other examples of isocaudomers include: BamHI/BclI/BglII/BstYI/DpnII
NcoI/BspHI/FatI/PciI
NdeI/AseI/BfaI/Csp6I/MseI
XbaI/AvrII/NheI/SpeI/StyI
XhoI/PspXI/SalI


References


See also

Enzymes Restriction enzymes {{enzyme-stub