Human erythrocyte pyrimidine 5 '-nucleotidase, PN-I, is identical to p36, a protein associated to lupus inclusion formation in response to alpha-interferon

Erythrocyte maturation is accompanied by RNA degradation and release of mon onucleotides. We have previously purified PN-I, a pyrimidine nucleotidase w hose deficiency is associated with hemolytic anemia. Computer-aided analysi s of PN-I tryptic and CNBr peptide sequences revealed substantial identity with tryptic peptide sequences reported for p36, an alpha-interferon-induce d protein, PN-I partial sequences were matched through the expressed sequen ce tag database with different human complementary DNA(cDNA) clones, whose sequences were exploited to screen a human placenta cDNA library. PN-I cDNA , coding for a 286-residue protein, was expressed in Escherichia coli, yiel ding a fully active recombinant enzyme. The recombinant protein sequence co mprised the peptide sequences determined for PN-I and p36. Rabbit antisera raised against two peptides deriving from p36 and PN-I tryptic digestions, respectively, recognized both wild-type and recombinant PN-I. Molecular pro perties of the two proteins were essentially the same. We conclude that p36 and PN-I are identical proteins, (Blood. 2000;96:1596-1598) (C) 2000 by Th e American Society of Hematology.