ADP-ribose, ADPR

ADP (Adenosine diphosphate) 536 in adenylate system 302 - 304 complexes with metal ions 296 dissociation as acid 288 intracellular concentration 304 P-31 NMR spectrum 642 pka value of 293 in regulation 535 ADP-ribose (ADPR) 315, 778, 780 ADP-ribosylation 545, 778 ADP-ribosylation factors (ARFs) 559 Adrenaline (epinephrine) 534, 542, 553, 553s in adrenergic receptor 535 a-Adrenergic receptors 553, 558, 563 p-Adrenergic receptors 553, 554 in asthma 553 in heart failure 553 receptor kinase 553 structure (proposed) 534, 555 topology 555... 

Diphtheria toxin is composed of two protein subunits. The B subunit binds to a cell surface receptor, facilitating the entry of the A subunit into the cell. In the cell, the A subunit catalyzes a reaction in which the ADP-ribose (ADPR) portion of NAD is transferred to EF2 (ADP-ribosylation). In this reaction, the ADPR is covalently attached to a post-translationally modified histidine residue, known as diphthamide. ADP-ribosylation of EF2 inhibits protein synthesis, leading to cell death. Children, including Erna Nemdy s daughter, are usually immunized against this often fatal disease at an early age. 

Mono- and poly-ADP-ribosylation. Mono-ADP-ribosylation and poly(ADP-ribose) modification catalyzed by ADP-ribosyl transferase and poly(ribose) synthetase respectively, append mono- and poly ADP-ribose (ADPR) moieties (Hayaishi and Ueda, 1977). In poly ADPR, the polymeric chain consists of woADP-ribose, 2 -(5"-phosphoribosyl)-5 -AMP... 

Abbreviations 3AB 3-aminobenzamide ADPR ADP-ribose AMD Automodification domain ... 

Poly(ADP-ribose) (PAR) is a heterogenous branched polymer of repeating ADPR units linked via glycosidic ribose-ribose 1" 2 bonds in the linear chain and... 

Figure 3. Proposed pleiotropic functions carried out by nuclear ADP-ribosylation reactions. Events such as cellular proliferation, differentiation, transformation, and DNA damage caused by external agents (e.g., ionizing radiation, drugs) involve changes in the integrity of DNA and/or chromatin architecture (a) which activate the poly(ADP-ribose) polymerase to catalyze the ADP-ribosylation of nuclear proteins predominantly at the expense of cytoplasmic NAD (b). The consequences of protein ADP-ribosylation are a decrease in cellular NAD content, alterations in chromatin structure, and possibly also the activity of various enzymes involved in chromatin function (c). This tripartite system operates, either wholly or partly, to ameliorate the activation of the polymerase by modulating the repair of DNA strand breaks, thereby affecting those processes which initially triggered the activation of the enzyme (d). Pr, protein NAm, nicotinamide (ADPR) , poly(ADP-ribose). (From Gaal and Pearson, 1986).

The tumoverofADPRpolymer residues is effeaedby poly(ADP-ribose) glycohydrolase (PARC) which catalyses hydrolysis of both linear and branched polymer residues yieldii free ADPR. ... 

Early studies of ADP-ribose polymer metabolism concluded that PARG was unable to remove the protein proximal ADPR residue from acceptor proteins. This led to the isolation of an ADP-rlbosyl protein lyase that catalyzes removal of the protein proximal ADPR residue linked to the acceptor protein. Although this enzyme was discovered many years ago, it has received very little attention and consequently its structure function relationships and role in ADPR polymer metabolism are still poorly understood. Additional questions have been raised by recent studies that indicate that PARG can catal removal of protein proximal ADPR residues linked to carboxylate groups of histone HI. It is possible that the property of both enzymes to catalyze removal of these residues represents redundancy in function or that specific polymer acceptor proteins require different enzymes to catalyze removal. 

Fig. 2. Effect of ethanol on calf thymus poly(ADP-ribose) synthetase. Initial velocities were obtained by incubating partially purified enzyme with 100 juM [ PJNAD in 0.2 ml reactions containing 50 vnM Tris-HCl, pH 8.0, 5 mAf EDTA, and 0.06 Mg Hae III fragments with 5 -hydro-xyls (A), 0.3 Mg ml Hae III fragments with 5 -phosphates ( ), or 3 Mg ml Hpa II fragments (°). The results of one representative experiment are shown and the data for each DNA are expressed as activity relative to the activity in the absence of ethanol (165, 183, 137 pmol ADPR/2 min, respectively)...

Poly(ADP-ribose) polymerase activity can be dissociated from the free mRNP particles by a high KQ concentration, as described for free mRNP associated kinases [5]. 0.6 M KQ is needed to entirely separate the poly(ADPR) polymerase activity from the mRNA, indicating that the enzyme is tightly associated with the particle. Moreover, the released enzyme becomes insensitive to RNase A (data not shown). 

Neither transfer of single ADPR residues by specific eukaryotic transferases nor the existence of other than ester-type linkages in ADPR protein conjugates were recognized for a number of years [24]. Now, there is increasing evidence that the eukaryotic cell possesses a rather elaborate instrumentarium of ADP-ribosylation reactions to modulate important processes. The use of mono(ADPR) groups for the covalent modification of protein provides a tool that may prove to be as versatile as poly(ADP-ribosyl)ation. In addition to the systems discussed here (alkylated cells, differentiation, tumor promotors), mono(ADP-ribosyl)ation may be involved also in the modulation of protein synthesis [8], in the response to heat shock (M. Jacobson, personal communication), and in glutamine synthesis [25]. Nonenzymic mono(ADP-ribosyl)ation reactions must also be taken into consideration whenever the functions of active (P)ADP-ribose as present in the pyridine nucleotides are studied. Finally, preliminary data may indicate that an additional way to modulate protein functions could be provided by phospho-(ADP-ribosylation) reactions. 

To confirm that the 1.3 kb insert from lambda gtll encoded poly(ADP-ribose) polymerase, the insert was used to screen a 3- to 4-kb subset of a transformed human fibroblast cDNA library in the Okayama-Berg vector. One of the vectors, clone pcD-12 yielded a BamR fragment within the additive size 3.6-7 kb, which corresponded with the size of mRNAs noted earlier for poly(ADP-ribose) polymerase. This vector [pcD-poly(ADPR)p]... 

Fig. 2. Nucleotide sequence of the Okayayma-Berg pcD>poly(ADPR)p cDNA insert and the deduced amino acid sequence of the 113, 135-kDa protein. The protein contains sequences coding for three poly(ADP-ribose) polymerase peptides (underlined and sequentially numbered), in the 3 untranslated region a putative mRNA processing signd (AATAAA) is underlined. In the 5 region two nucleotides that correspond to the Kozak criteria for initiation are underlined. (Taken from Ref. 3).

Large poly(ADPR) Protein Fig, 5. A proposed model of poly(ADP-Processive (Rapid) I ribose) glycohydrolase action on... 

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