Random mutagenesis of the poly(ADP-ribose) polymerase catalytic domain reveals amino acids involved in polymer branching

Biochemistry. 1997 Oct 7;36(40):12147-54. doi: 10.1021/bi971055p.


Poly(ADP-ribose) polymerase (PARP) is a multifunctional nuclear zinc finger protein which participates in the immediate response of mammalian cells exposed to DNA damaging agents. Given the complexity of the poly(ADP-ribosylation) reaction, we developed a large-scale screening procedure in Escherichia coli to identify randomly amino acids involved in the various aspects of this mechanism. Random mutations were generated by the polymerase chain reaction in a cDNA sequence covering most of the catalytic domain. Out of 26 individual mutations that diversely inactivated the full-length PARP, 22 were found at conserved positions in the primary structure, and 24 were located in the core domain formed by two beta-sheets containing the active site. Most of the PARP mutants were altered in poly(ADP-ribose) elongation and/or branching. The spatial proximity of some residues involved in chain elongation (E988) and branching (Y986) suggests a proximity or a superposition of these two catalytic sites. Other residues affected in branching were located at the surface of the molecule (R847, E923, G972), indicating that protein-protein contacts are necessary for optimal polymer branching. This screening procedure provides a simple and efficient method to explore further the structure-function relationship of the enzyme.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amino Acids / chemistry*
  • Amino Acids / genetics*
  • Catalysis
  • Humans
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Poly(ADP-ribose) Polymerases / chemistry*
  • Poly(ADP-ribose) Polymerases / genetics*
  • Polymerase Chain Reaction
  • Polymers / chemistry*
  • Protein Structure, Tertiary*
  • Structure-Activity Relationship


  • Amino Acids
  • Polymers
  • Poly(ADP-ribose) Polymerases