BamHI

BamHI (pronounced "Bam H one") (from Bacillus amyloliquefaciens) is a type II restriction endonuclease, having the capacity for recognizing short sequences (6 bp) of DNA and specifically cleaving them at a target site. This exhibit focuses on the structure-function relations of BamHI as described by Newman, et al. (1995). BamHI binds at the recognition sequence 5'-GGATCC-3', and cleaves these sequences just after the 5'-guanine on each strand. This cleavage results in sticky ends which are 4 bp long. In its unbound form, BamHI displays a central b sheet, which resides in between α-helices.

BamHI undergoes a series of unconventional conformational changes upon DNA recognition. This allows the DNA to maintain its normal B-DNA conformation without distorting to facilitate enzyme binding. BamHI is a symmetric dimer. DNA is bound in a large cleft that is formed between dimers; the enzyme binds in a "crossover" manner. Each BamHI subunit makes the majority of its backbone contacts with the phosphates of a DNA half site but base pair contacts are made between each BamHI subunit and nitrogenous bases in the major groove of the opposite DNA half site. The protein binds the bases through either direct hydrogen bonds or water-mediated H-bonds between the protein and every H-bond donor/acceptor group in the major groove. Major groove contacts are formed by atoms residing on the amino-terminus of a parallel 4 helix bundle. This bundle marks the BamHI dimer interface, and it is thought that the dipole moments of the NH2-terminal atoms on this bundle may contribute to electrostatic stabilization.