Chang Y M, Lin S, Liao T H
Institute of Biochemistry, National Taiwan University/College of Medicine, Taipei.
Biotechnol Appl Biochem. 1994 Feb;19(1):129-40.
DNAase F is a minor isoform of bovine pancreatic DNAase which can be separated from the other isoforms (DNAases A, B, C and D) present in a commercial preparation by a preparative isoelectric-focusing cell (Rotofor; Bio-Rad). The ampholytes and other contaminating proteins present in DNAase F preparations can be removed by chromatography on an affinity column (Cibacron Blue 3GA-agarose) and a hydrophobic-interaction column (phenyl-Sepharose CL-4B). The complete separation of DNAase F from the other isoforms is demonstrated on a thin-layer isoelectric-focusing gel, DNAase F being the most basic (pI 5.68). A procedure is described for tryptic peptide mapping by h.p.l.c. requiring only picomolar amounts of DNAase F protein. The DNAase F map shows two peptide peaks 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 normally eluted. The amino acid compositions and sequences for the two new peptides suggest that Gly240 in DNAase A is changed to Arg240 in DNAase F.
