Molecular, biochemical and immunological studies of hen pancreatic deoxyribonuclease I

Deoxyribonuclease I (DNase I) was purified from the hen pancreas to electro phoretic homogeneity using six-step column chromatography. The purified enz yme showed a molecular mass of about 33 kDa and maximum activity at pH 7.0. It required divalent cations, Mg2+ and Ca2+, for its activity and was inhi bited by EDTA, EGTA and an antibody specific to the purified enzyme but not by G-actin. A 1066-bp cDNA encoding hen DNase I was constructed from the t otal RNA of a hen pancreas using a combination of the reverse transcriptase -polymerase chain reaction and rapid amplification of cDNA ends methods, fo llowed by sequencing. The cDNA was expressed in Escherichia coli, and the r ecombinant polypeptide exhibited significant enzyme activity. The mature he n DNase I protein was found to consist of 262 amino acids. In human and bov ine DNase I four amino acid residues, Glu-13, Tyr-65, Val-67 and Ala-114 ar e involved in actin binding, whereas in the hen DNase I these positions wer e occupied by Asp, Phe, Ser and Phe, respectively. A survey of the DNase I distribution in 15 hen tissues showed that the pancreas had the highest lev els of both DNase I enzyme activity and DNase I gene expression. The result s of our phylogenetic and immunological analyses indicate that the hen DNas e I is not closely related to the mammalian enzymes. This is the first repo rt in which has been described the results of molecular, biochemical and im munological analyses on hen DNase I. (C) 1999 Elsevier Science Ltd. All rig hts reserved.