Purification, cloning and nucleotide sequence determination of cynomolgus monkey apolipoprotein C-II: comparison to the human sequence.

We have purified apolipoprotein C-II (apo C-II) from cynomolgus monkey plasma, prepared antibody against it and used the antibody to isolate a cDNA containing the complete coding sequence for cynomolgus monkey apo C-II. Sequence analysis indicated that the monkey apo C-II cDNA was 200 bp longer than the human and the difference in size was all in the 5 degrees untranslated region of mRNA. This was confirmed by Northern analysis of human and monkey RNA. There was an open reading frame in the monkey apo C-II cDNA sequence encoding a preprotein of 101 amino acids - identical in size to the human protein. The carboxyl terminal 44 amino acids of the protein were 100% homologous to the human apo C-II amino acid sequence indicating evolutionary conservation of both structure and function. However, the amino terminal 35 amino acids of the protein were only 75% homologous and the amino terminal 19 amino acids were only 58% homologous to the human sequence. The amino acid sequence derived from the nucleotide sequence predicts a more basic protein than the human apo C-II and this is confirmed by isoelectric focusing and immunoblotting.