The effects of the amino, hydroxyl, imidazole and carboxyl groups of Ser His on DNA cleavage reaction were studied. It was found that the amino and hydroxyl groups were essential for the DNA cleavage activity of Ser His, and that anyone of them blocked would result into the loss of cleavage activity. The carboxyl group was not the necessary group. The presence of the imidazole group would enhance the cleavage activity. However, the histidyl serine dipeptide, as the formula isomer of Ser His with the inverse peptide sequence, could not cleave DNA at all. Based on the above experimental results, a presumed cleavage mechanism of Ser His on DNA was proposed. [WT5HZ]
Linear and supercoiled DNA were cleaved by HPLC purified seryl histidine dipeptide(SH). It was found that the DNA fragments produced by the reaction of SH and DNA could be ligated together by T 4 DNA ligase. This result implied that the SH was the first example of the ion free artificial DNA cleavage agent that could split DNA by hydrolysis mechanism.
