Proteins ADP ribosylation

Cholera toxin, heat labile coli toxins Gs proteins ADP-ribosylation Activation of adenylate cyclase (cholera, traveler -d iarrhea)... 

Pertussis toxin Gj,0 proteins ADP-ribosylation Inhibition ofG protein signaling (whooping cough)... 

C. botulinum C3-toxin and related toxins Rho proteins ADP-ribosylation Inhibition of RhoA, B,C Destruction of the cytoskeleton... 

Cholera toxin catalyzes the ADP-ribosylation of a specific arginine residue in G and Gat. This covalent modification inhibits the intrinsic GTPase activity of these a subunits and thereby freezes them in their activated, or free, state (Fig. 19-1C). By this mechanism, cholera toxin stimulates adenylyl cyclase activity and photoreceptor transduction mechanisms. The ability of cholera toxin to ADP-ribosylate G may require the presence of a distinct protein, ADP-ribosylation factor (ARF). ARF, which is itself a small G protein (Table 19-2), also is ADP-ribosylated by cholera toxin. ARF is implicated in controlling membrane vesicle trafficking (see Ch. 9). 

Bentley, J.K., Garbers, D.L., Domino, S.E., Noland, T.D., and Van Dop, C. (1986). Spermatozoa contain a guanine nucleotide-binding protein ADP-ribosylated by pertussis toxin. Biochem. Biophys. Res. Commun. 738 728-734. 

Reversibility A Fundamental Requirement of a Metabolic Regulatory Process Functions of Protein ADP-ribosylation... 

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).

Release of Cs from rat liver mitochondria is induced by oxidation of mitochondrial pyridine nucleotides, but also requires that these be cleaved into ADP-ribose and nicotinamide. Mitochondrial protein ADP-ribosylation has been proposed as the link between this cleavage and Ca " " release (Figure 9). Recent work... 

Native protein ADP-ribosylated protein T 1/2 of proteolysis Activators... 

The enhancement of ADPR-transferase activity is also an early consequence of drug-exposure and leads to defined changes in protein ADP-ribosylation, although the significance of these changes remains unclear at this time. The kinetics of cell death during exposure to methotrexate are similar when hypoxanthine is also present (when the activation of transferase is prevented but the basal activity is still present Fig. 2), or when SAB is present with the methotrexate. 

Oxidation alone of pyridine nucleotides is not sufficient to induce Ca release. In the presence of ATP, the hydroperoxide-induced pyridine nucleotide oxidation is even accelerated, yet pyridine nucleotide hydrolysis and Ca release are inhibited [11]. Similar observations were made during the menadione-induced Ca release [10]. When liver mitochondria are treated with N-ethyl maleimide to lower intramitochondrial glutathione, both oxidation of pyridine nucleotides and Ca " release are inhibited (S. Baumhuter, C. Richter, unpubl.). Finally, both pyridine nucleotide hydrolysis and Ca release show the same sigmoidal dependence on the mitochondrial Ca load [15]. Thus, there is clear, albeit circumstantial, evidence that pyridine nucleotide hydrolysis and Ca " release are functionally related. The link between the two processes may be protein ADP-ribosylation. 

In view of die mitochondrial autonomy and the existence of cell division independent neobiogenesis of these organelles it seems likely that in some respect mitochondrial ADP-ribosylation plays a role similar to that of nuclear ADP-ribosylation. There seems to exist certain links between ADP-ribosylation and mitochondrial replication. Our preliminary experiments showing an increase of ADP-ribosyl transferase activity during mitochondrial neobiogenesis are in favor of an involvement of ADP-ribosylation in mitochondrial replication. The topographical association of a part (25%) of protein ADP-ribosylation and mitochondrial DNA polymerase activities does also suggest such a relationship (11). 

In rat liver most of the cellular mono(ADP-ribosylated) proteins are associated with the mitochondrial fraction (1). Two mono(ADP-ribosyl)ating systems have been described in mitochondria, one in die soluble (matrix) fraction (2, 3), the other in submitochondrial particles (SMP, inverted inner membrane vesicles) (3, 4). The ADP-ribosylated matrix protein has a molecular mass of 100 kDa and appears to consist of two major subunits of equal mass. In SMP of both rat liver (4) and beef heart (3), there is one major acceptor protein for mono(ADP-ribose), which migrates with an apparent molecular mass of 30 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Mono(ADP-ribosylation) of the acceptor protein of beef heart SMP was suggested to occur non-enzymicaUy (3). In rat liver SMP, ADP-ribosylation of the 30 kDa protein most probably occurs at an arginine residue, and is readily reversible in the presence of ATP (4). The characteristics of this ADP-ribosylation reaction, i.e. protein specificity and sensitivity to ATP, together widi the observation that intramitochondrial hydrolysis of NAD(P)+ is accompanied by release of Ca + from mitochondria suggests a functional link between mitochondrial protein ADP-ribosylation and Ca2+ release (5,6). 

Using a newly developed fluorescent technique (7,8) we have investigated protein ADP-ribosylation in intact mitochondria. Our findings indicate the existence of at least three classes of ADP-ribosylated proteins in rat liver mitochondria and give evidence for a transient increase of protein-bound mono(ADP-ribose) during the NAD(P)+- linked Ca + release. 

Antonny, B., Beraud-Dufour, S., Chardin, P., and Chabre, M. (1997). N-terminal hydrophobic residues of the G-protein ADP-ribosylation factor-1 insert into membrane phospholipids upon GDP to GTP exchange. Biochemistry 36, 4675-4684. 

Robineau, S., Chabre, M., and Antonny, B. (2000). Binding site of brefeldin A at the interface between the small G protein ADP-ribosylation factor 1 (ARFl) and the nucleotide-exchange factor Sec7 domain. Proc. Nad. Acad. Sci. USA 97, 9913-9918. 

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