FUNCTIONAL-CHARACTERIZATION OF A HUMAN DNASE-LIKE PROTEIN ENCODED BY A GENE POSITIONED IN XQ28

Xib, a gene recently reported to reside on the q28 region of the human X chromosome [Pergolizzi et al. (1996) Gene 168, 267-270], contains a n open reading frame homologous to those of the DNase I family enzymes . The full open reading frame of this gene has been fused to the E. co li gene of the maltose binding protein and expressed in bacteria as a chimeric protein. The partially purified chimeric protein is enzymatic ally active. It introduces single and double stranded breaks into supe rcoiled DNA, at 30 degrees C in the absence of divalent cations and at a pH optimum of 5.2. To our knowledge this enzyme represents the firs t cloned human endonuclease with characteristics similar to those of a cidic DNase II.