Restriction Enzymes: Tools in Clinical Research

Restriction enzymes (or restriction endonucleases) are bacterial enzymes capable of cleaving double-stranded DNA. Even though the enzymes are bacterial in origin, because of the universal nature of DNA they can digest DNA from any species, including humans. Importantly, restriction enzymes (REs) carry out this cleavage at specific sites in DNA governed by the sequence context (so-called recognition sequences). Hence, REs are known to be extremely sequence-specific; subtle alterations in the recognition sequence render the sites indigestible. This fact is the basis of their usefulness in clinical research and diagnostics. Table 1 is a list of a few of the common REs showing their sequence specificities. Figure 1 shows the interaction of a RE with DNA. The RE interacts with DNA via multiple hydrogen bonds (typically 10/2-15) plus numerous van der Waals interactions. Only when the RE-DNA complex is tightly bound does the catalytic domain cause DNA cleavage (2 ).