Human placenta DNA primase: purification of enzyme and analysis of RNA primer synthesis

Biochem Int. 1991 Apr;23(6):1195-204.


The immunoaffinity purification of human placenta DNA primase devoid of DNA polymerase alpha activity is described. Primase consists of 52 and 59 kDa polypeptides. They form a single protein of 330 kDa under native conditions. The polypeptide structure of primase is believed to be (52 + 59)3. Primase synthesizes the oligoribonucleotides 2-9 monomers long and multimeric oligoribonucleotides of a modal length of about 10 monomers. The following model of RNA primer synthesis is proposed: 1) primase, being in free state or in complex with Pol alpha, forms a protein trimer or another structure that includes several primases; 2) primase synthesizes de novo only the oligonucleotides 2-10 monomers in length; 3) the newly synthesized oligonucleotides dissociate in solution or translocate to either Pol alpha or a neighbouring primase unit to be further elongated with the next 7-10 mononucleotides.

MeSH terms

  • Chromatography, Affinity
  • DNA Primase
  • DNA Replication
  • Electrophoresis, Polyacrylamide Gel
  • Humans
  • Models, Biological
  • Placenta / enzymology*
  • Protein Denaturation
  • RNA / biosynthesis*
  • RNA Nucleotidyltransferases / isolation & purification*
  • RNA Nucleotidyltransferases / metabolism


  • RNA primers
  • RNA
  • DNA Primase
  • RNA Nucleotidyltransferases