Ribosylation, ADP

ADP-Ribosyl transferase (from human placenta) [9026-30-6]. Purified by making an affinity absorbent for ADP-ribosyltransferase by coupling 3-aminobenzamide to Sepharose 4B. [Burtscher et al. Anal Biochem 152 285 1986.]... 

Small GTPases of the Rho family are ADP-ribosylated (e.g., at Asn4l of RhoA) and inactivated by C3-like toxins from Clostridium botulinum, Clostridium limosum, and Staphylococcus aureus. These proteins have a molecular mass of 23-30 kDa and consist only of the enzyme domain. Specific inhibition of Rho functions (Rho but not Rac or Cdc42 are targets) is the reason why C3 is widely used as a pharmacological tool [2]. 

Diphtheria toxin, Pseudomonas exotoxin A Elongation factor 2 ADP-ribosylation Inhibition of protein synthesis (diphtheria, Pseudomonas infection)... 

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 C2-toxin and related toxins Actin ADP-ribosylation Inhibition of actin polymerization... 

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

Cholera toxin is a protein toxin of Vibrio choleme. Toxin ADP-ribosylates the a-subunit of the Gs heterotrimeric... 

GTP-binding protein at an arginine residue which is involved in GTP hydrolysis. ADP-ribosylation thus leads to constitutive activation of Gs. 

Nucleotidylation - the addition of adenylate-residues by Lnu enzymes - can also be the cause of resistance to lincosamide antibiotics in staphylococci and enterococci. A plasmid encoded ADP-ribosylating transferase (Arr-2) that leads to rifampicin resistance has been detected in various Enterobacteriaceae as well as in Pseudomonas aeruginosa. 

Researchers found that NAD serves as a substrate in poly(ADP-ribose) synthesis, a reaction important for DNA repair processes. In addition, it takes part in mono (ADP-ribosyl)ation reactions that are involved in endogenous regulation of many aspects of signal transduction and membrane trafficking in eukaryotic cells. 

Pertussis toxin is produced by the bacterium Bordetella pertussis. It covalently modifies G-proteins of the G/Go family (transfer of a ADP-ribose moiety of NAD onto G-protein a-subunits). ADP-ribosylated G-proteins are arrested in their inactive state and, as a consequence, functionally uncoupled from their respective effectors. Examples for pertussis toxin-sensitive cellular responses include the hormonal inhibition of adenylyl cyclases, stimulation ofK+ channels, inhibition of Ca2+ channels and stimulation ofthe cGMP-phosphodiesterase in retinal rods. 

Secondly, treatment of neutrophils with pertussis toxin, which ADP-ribosylates a neutrophil G protein and causes a loss of cell responsiveness via receptor-mediated pathways (40,41), has minimal effect on the response to HCH (Figure 11, lower panel). Thus it can be concluded that HCH activation of neutrophils is independent of receptor-mediated activation of G proteins. 

Diphtheria toxin, an exotoxin of Corynebacterium diphtheriae infected with a specific lysogenic phage, catalyzes the ADP-ribosylation of EF-2 on the unique amino acid diphthamide in mammalian cells. This modification inactivates EF-2 and thereby specifically inhibits mammalian protein synthesis. Many animals (eg, mice) are resistant to diphtheria toxin. This resistance is due to inability of diphtheria toxin to cross the cell membrane rather than to insensitivity of mouse EF-2 to diphtheria toxin-catalyzed ADP-ribosylation by NAD. 

In addition to its coenzyme role, NAD is the source of ADP-ribose for the ADP-ribosylation of proteins and polyADP-ribosylation of nucleoproteins involved in the DNA repair mechanism. 

McLaren J, Boulikas T, Vamvakas S. 1994. Induction of poly(ADP-ribosyl)ation in the kidney after in vivo application of renal carcinogens. T oxicology 88 101-112. 

Post-translational modification of proteins plays a critical role in cellular function. For, example protein phosphorylation events control the majority of the signal transduction pathways in eukaryotic cells. Therefore, an important goal of proteomics is the identification of post-translational modifications. Proteins can undergo a wide range of post-translational modifications such as phosphorylation, glycosylation, sulphonation, palmitoylation and ADP-ribosylation. These modifications can play an essential role in the function of the protein and mass spectrometry has been used to characterize such modifications. 

FIGURE 7.7 C-terminal residues of G-protein a subunits. The cysteine ADP-ribosylated by Pertussis toxin (PTx) is boxed. 

The first G-protein a subunit to be identified was Gs. The a subunit of Gs (as) is responsible for stimulating adenylate cyclase (hence, the subscript s ) and is ADP-ribosylated and activated by CTx. Gs has at least four molecular variants. Some evidence exists that as can also enhance the activity of cardiac L-type Ca2+ channels, independently of their phosphorylation by cAMP-stimu-lated protein kinase A. Golf is a cyclase-stimulating homolog in the olfactory epithelium, activated by the large family of olfactory receptors. 

G, is the G-protein responsible for inhibiting adenylate cyclase. The inhibition is mediated by the a subunit. Unlike Gs, G, is not affected by CTx but instead is ADP-ribosylated (and inhibited) by PTx. Of the three isoforms of G, (Gn 3), an is the most potent inhibitor of cyclase. G, also activates inward-rectifier (Kir3.1/3.2 and Kir 3.1/3.4) K+ channels (GIRK channels), and this activation is mediated by released f v subunits (see below). 

Gq and Gn are two closely related and widely distributed G-proteins whose a subunits stimulate PLC. They are not ADP-ribosylated by either PTx or CTx, so they are probably responsible for many instances of PTx-insensitive PLC stimulation. G14 and G15 are two more distantly related PTx-insensitive G-proteins that can stimulate PLC. G12 and G13 are other PTx-insensitive G-proteins related to Gq, while Gz is more closely related to G, the precise functions of these G-proteins are not yet clear. Though of restricted distribution (to hemopoietic-derived cells), G16 is interesting because it lacks receptor specificity and so acts as a universal PLC transducer. 

Singh AK. 1993. Effects of chronic low-level lead exposure on mRNA expression, ADP-ribosylation and photoaffmity labelling with [ -32P]guanine triphosphate -y -azidoanilide of GTP-binding proteins in neurons isolated from the brain of neonatal and adult rats. Biochem Pharmacol 45 1107-1114. 

Protein modification 36 Variable Acetylation, fatty acylation, glycosylation, methylation, phosphorylation, ADP-ribosylation, ubiquitination, proteolytic digestion... 

Carty, D. J. (1994). Pertussis toxin-catalyzed ADP-ribosylation of G proteins. Meth. Enzymol. 237, 63-70. 

Genomic sequence analysis has identified 17 structurally related proteins containing a PARP catalytic domain [3] however, closer inspection suggests that only PARPs 1-3, PARP-4 (vault PARP), and tankyrases 1 and 2 may truly function as poly(ADP-ribosyl)ating proteins. The remaining... 

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