An endo-exonuclease from meiotic tissues of the basidiomycete Coprinus cinereus. Its purification and characterization.

An endo-exonuclease has been identified and partially purified from the basidiocarp tissues of the basidiomycete Coprinus cinereus, which include synchronous meiosis at karyogamy-pachytene stages. Its peak activity appears during the meiotic prophase. The Coprinus endo-exonuclease has a single-strand specific endonuclease activity that converts the supercoiled DNA to relaxed DNA. The endonucleolytic cleavage of single-strand DNA generates 3'-phosphomonoester termini. It is also a single-strand-specific exonuclease and it hydrolyzes linear DNA in a 3' to 5' direction, but is unable to hydrolyze single-strand DNA having a 3'-phosphomonoester terminus. It requires Mg2+ with an optimal concentration of 25 mM. It has an optimal pH of 8.3, a peak enzyme activity at 50 degrees C, and it contains a single 43-kilodalton polypeptide. Coprinus meiotic endo-exonuclease may be involved in the substrate preparation for meiotic recombination.