Production of Site Specific Nucleases - Restriction Enzymes - The DNA recognition and binding properties of proteins can be combined using chemical cleavage agents. Cys¹⁷⁸ of E. coli CAP protein; has been modified using 'S-iodoacetamide -1, 10- phenanthroline' yielding a DNA cleaving agent that recognized and cleaved DNA at the centre of the recognition site (22 bp) for CAP.

This may give restriction enzymes recognizing upto 20 bases instead of 6 or 8 bases and may, therefore, be useful for isolating long DNA fragments needed for sequencing and mapping. Nucleases may also be produced by fusion of non-specific phosphodiesterases to oligonucleotides of defined sequence.

For a nuclease from Staphylococcus modified by this approach, it was shown that oligonucleotide component of fused product pairs with its complementary sequence and the hybrid enzyme hydrolyses single stranded DNA or RNA adjacent to the oligonucleotide binding site. This approach thus can also be used for developing artificial restriction enzymes.