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Microbiology

Function of hindiii?

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July 26, 2009 11:04PM

Haemophilus influenzae is a species of bacteria that is the source of the HindIII restriction enzyme that cleaves the palindromic DNA sequence 5'-AAGCTT-3' in the presence of the cofactor Mg2+ via hydrolysis. While restriction enzymes cleave at specific DNA sequences, they are first required to bind non-specifically with the DNA backbone before localizing to the restriction site. On average, the restriction enzyme will form 15-20 hydrogen bonds with the bases of the recognition sequence. With the aid of other Van der Waals interactions, this bonding facilitates a conformational change of the DNA-enzyme complex which leads to the activation of catalytic centers. Despite the lack of evidence suggesting an exact mechanism for the cleavage of DNA by HindIII, site-mutagenesis analysis coupled with more detailed studies of metal ion-mediated catalysis in EcoRV have led to the following proposed catalytic mechanism. It has been suggested that during the hydrolysis of DNA by EcoRV the catalytic residue Lys-92 stabilizes and orients the attacking water nucleophile, while the carboxylate of Asp-90 stabilizes the leaving hydroxide anion through to coordination of Mg2