Complete cDNA Sequence of Human Preceruloplasmin

A cDNA for human ceruloplasmin (EC 1.16.3.1) was identified in a human liver cDNA library by screening with two mixtures of synthetic oligodeoxyribonucleotides that were complementary to two regions of ceruloplasmin mRNA as predicted from the amino acid sequence of plasma ceruloplasmin. The resulting clone (phCP1) contained DNA coding for amino acid residues 202-1046 of the protein, followed by a stop codon, a 3′ untranslated region of 123 base pairs, and a poly(A) tail. To isolate cDNAs encoding the 5′ end of ceruloplasmin mRNA, a cDNA library was constructed in λ gt10. The cDNA for this library was synthesized by reverse transcription of human liver poly(A)+ RNA, using random oligonucleotides as primers. When this cDNA library was screened by using a 5′ fragment of phCP1 as a hybridization probe, several positive clones were identified. One of these clones (λ hCP1) contained DNA coding for a probable signal peptide of 19 amino acid residues followed by DNA coding for residues 1-380 of plasma ceruloplasmin. Blot hybridization analysis showed that ceruloplasmin mRNA from human liver and the human hepatoma cell line HepG2 is 3700 nucleotides in size. Liver contained an additional mRNA species that is like ceruloplasmin mRNA and is 4500 nucleotides in size. Comparison of the complete nucleotide sequences of human ceruloplasmin cDNA and human clotting factor VIII cDNA showed regions of sequence homology, suggesting that these two proteins have evolved from a common ancestor.