BAL 31 nuclease as a probe in concentrated salt for the B-Z DNA junction

Abstract

The BAL 31 nuclease, an extracellular nuclease from A . eapejiana , specifically recognizes and cleaves the salt induced conformational junction between B and Z–DNA. Short segments of (dC–dG) left-handed Z–helix, comprising ˜1% of the total DNA, are specifically detected within two different recombinant plasmids. The BAL 31 enzyme is highly resistant to inactivation by the presence of high concentrations of a variety of electrolytes that stabilize left–handed helices, is active at physiological pH, and can be used to probe both linear and circular DNAs. Additionally, the nuclease cleaves left-handed (dC–dG)n only very poorly, if at all. Thus, the BAL 31 nuclease can be utilized as a probe for helical junctions and consequently for segments of left–handed DNA that might exist within predominantly right–handed naturally occurring genomes.