Principles and Processes of Biotechnology

W. Arber, H. Smith, and D. Nathan

The 1978 Nobel Prize in Physiology or Medicine was awarded to Werner Arber, Hamilton Smith, and Daniel Nathan for the discovery and application of restriction enzymes. Kary Mullis won the 1993 Nobel (Chemistry) for PCR.

HindII

HindII was the first restriction enzyme discovered, isolated from Haemophilus influenzae Rd by Hamilton Smith. EcoRI (from E. coli), BamHI, and HindIII were discovered later. Note: HindII produces blunt ends, while HindIII produces sticky ends.

A sequence that reads the same 5'→3' on both complementary strands

In DNA, a palindromic sequence reads identically in the 5'→3' direction on both complementary strands. For example, EcoRI's recognition site 5'-GAATTC-3' on the top strand — reading the complementary (bottom) strand 5'→3' also gives GAATTC. This symmetry is what restriction enzymes recognise.

Joins DNA fragments by forming phosphodiester bonds

DNA Ligase catalyses the formation of a covalent phosphodiester bond between the 3'-OH and the 5'-phosphate ends of two adjacent DNA fragments. This 'glues' the fragments together — the opposite of what restriction enzymes do.