HindII is a type II restriction enzyme found in Haemophilus influenzae.
H.O. Smith, K.W. Wilcox, and T.J. Kelley, working at Johns Hopkins University in 1968, isolated and characterized the first restriction nuclease whose functioning depended on a specific DNA nucleotide sequence. Working with Haemophilus influenzae bacteria, this group isolated an enzyme, called HindII, that always cut DNA molecules at a particular point within a specific sequence of six base pairs. This sequence is:
5' G T ( pyrimidine: T or C) ( purine: A or G) A C 3' P3' C A ( purine: A or G) ( pyrimidine: T or C) T G 5'They found that the HindII enzyme always cuts directly in the center of this sequence. Wherever this particular sequence of six base pairs occurs unmodified in a DNA molecule, HindII will cleave both sugar-phosphate backbones of the DNA between the 3rd and 4th base pairs of the sequence. Moreover, HindII will only cleave a DNA molecule at this particular site. For this reason, this specific base sequence is known as the "recognition sequence" for HindII.