Hemophilus influenzae restriction endonuclease

The type II restriction endonucleases, which are the ones most widely used in molecular biology, are relatively small 50- to 100-kDa monomeric or dimeric proteins. About 2400 different enzymes with 188 different specificities had been isolated by 1995.83/84 The sites of attack, in most instances, are nucleotide sequences with a twofold axis of local symmetry.85 For example, the following sites of cleavage have been identified for two restriction endonucleases encoded by the DNA of R-factor plasmids of E. coli and for a restriction enzyme from Hemophilus influenzae. In the diagrams i are sites of cleavage, are sites of methyla-tion, and are local twofold axes (centers of palindromes) N can be any nucleotide with a proper base pairing partner. 

Danna, K. and Nathans, D. (1971) Specific cleavage of simian virus 40 DNA by restriction endonuclease of Hemophilus influenzae. Proc. Natl. Acad. Scl U.S.A., 68, 2913 -2917. 

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