BOVINE PANCREATIC DEOXYRIBONUCLEASE-F - ISOELECTRIC-FOCUSING, PEPTIDE-MAPPING AND PRIMARY STRUCTURE

DNAase F is a minor isoform of bovine pancreatic DNAase which can be s eparated from the other isoforms (DNAases A, B, C and D) present in a commercial preparation by a preparative isoelectric-focusing cell (Rot ofor; Bio-Rad). The ampholytes and other contaminating proteins presen t in DNAase F preparations can be removed by chromatography on an affi nity column (Cibacron Blue 3GA-agarose) and a hydrophobic-interaction column (phenyl-Sepharose CL-4B). The complete separation of DNAase F f rom the other isoforms is demonstrated on a thin-layer isoelectric-foc using gel, DNAase F being the most basic (pI 5.68). A procedure is des cribed for tryptic peptide mapping by h.p.l.c. requiring only picomola r amounts of DNAase F protein. The DNAase F map shows two peptide peak s not present in the DNAase A map, and the DNAase F map does not have a peak at the position where a C-terminal peptide of DNAase A is norma lly eluted. The amino acid compositions and sequences for the two new peptides suggest that Gly240 in DNAase A is changed to Arg240 in DNAas e F.