OVERPRODUCTION, PURIFICATION AND CHARACTERIZATION OF THE HPB12-L24 RIBOSOMAL-PROTEIN OF BACILLUS-SUBTILIS

HPB12-L24 was previously described as a bifunctional histone-like and ribosomal protein in Bacillus subtilis. In order to confirm the identi ty of HPB12 and L24, and to study the properties of this protein, the rplX gene of B. subtilis encoding L24 has been overexpressed in Escher ichia coli by an efficient protein overproduction system. A simple and rapid purification scheme using ammonium sulfate precipitation and ca tion-exchange chromatography is presented. 10 mg of pure L24 per g of Escherichia coli cells were obtained. The purified recombinant protein L24 is heat-stable, acid-soluble and binds preferentially supercoiled DNA like protein HPB12. These results confirm the identity of HPB12 a nd L24. Overexpression of rpIX led to gross alterations of cell morpho logy and to an abnormal shape of nucleoids.