The mechanism of the elongation and branching reaction of poly(ADP-ribose) polymerase as derived from crystal structures and mutagenesis.
The binding site for the acceptor substrate poly(ADP-ribose) in the elongation reaction of the ADP-ribosyl transferase poly(ADP-ribose) polymerase (PARP) was detected by cocrystallizing the enzyme with an NAD+ analogue. The site was confirmed by mutagenesis studies. In conjunction with the binding site of the donor NAD+, the bound acceptor reveals the geometry of the elongation reaction. It shows in particular that the strictly conserved glutamate residue of all ADP-ribosylating enzymes (Glu988 of PARP) facilitates the reaction by polarizing both, donor and acceptor. Moreover, the binding properties of the acceptor site suggest a mechanism for the branching reaction, that also explains the dual specificity of this transferase for elongation and branching, which is unique among polymer-forming enzymes.
Ruf
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Institut für Organische Chemie und Biochemie, Albertstr. 21, Freiburg im Breisgau, D-79104, Germany.
Rolli
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de Murcia
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Schulz
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D000246:Adenosine Diphosphate Ribose / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D002645:Chickens; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors; D006801:Humans; D008958:Models, Molecular; D016296:Mutagenesis; D009243:NAD / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D009536:Niacinamide / Q000031:analogs & derivatives; D010446:Peptide Fragments / Q000737:chemistry; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship
D004791:Enzyme Inhibitors; D010446:Peptide Fragments; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D009243:NAD; C055311:carbanicotinamide adenine dinucleotide; D000246:Adenosine Diphosphate Ribose; D009536:Niacinamide; D011065:Poly(ADP-ribose) Polymerases