Three conserved consensus sequences identify the NAD-binding site of ADP-ribosylating enzymes, expressed by eukaryotes, bacteria and T-even bacteriophages.
It has been previously reported that the three-dimensional structures of the NAD-binding and catalytic site of bacterial toxins with ADP-ribosylating activity are superimposable, and that the key amino acids for the enzymatic activity are conserved. The model includes an NAD-binding and catalytic site formed by an alpha-helix bent over a beta-strand, surrounded by two beta-strands bearing a Glu and a His, or Arg, that are required for catalysis. We show here that the model can be extended to comprise all proteins with ADP-ribosylating activity known to date, including all eukaryotic mono- and poly-ADP-ribosyltransferases, the bacterial ADP-ribosylating enzymes which do not have toxic activity, and the analogous enzymes encoded by T-even bacteriophages. We show that, in addition to the common Glu and Arg/His amino acids previously identified, the conserved motifs can be extended as follows: (i) the Arg/His motif is usually arom-His/Arg (where 'arom' is an aromatic residue); (ii) in the sequences of the CT group the beta-strand forming part of the 'scaffold' of the catalytic cavity has an arom-ph-Ser-Thr-Ser-ph consensus (where 'ph' represents a hydrophobic residue); and (iii) the motif centered in the key glutamic residue is Glu/Gin-X-Glu; while (iv) in the sequences of the DT group the NAD-binding motif is Tyr-X10-Tyr. We believe that the model proposed not only accounts for all ADP-ribosylating proteins known to date, but it is likely to fit other enzymes (currently being analysed) which possess such an activity.
Domenighini
M
M
IRIS, Chiron Biocine Immunobiological Research Institute in Siena, Italy.
Rappuoli
R
R
D036002:ADP Ribose Transferases / Q000737:chemistry*; D000595:Amino Acid Sequence; D001665:Binding Sites; D017124:Conserved Sequence; D008969:Molecular Sequence Data; D009243:NAD / Q000378:metabolism; D011065:Poly(ADP-ribose) Polymerases / Q000737:chemistry*
D009243:NAD; D036002:ADP Ribose Transferases; D011065:Poly(ADP-ribose) Polymerases