UMLS:C0043167 - FACTA Search

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Query: UMLS:C0043167 (pertussis)
19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The GTP-induced dissociation of T alpha from T beta gamma initiates the release of transducin from photolyzed rhodopsin and the subsequent activation of the cGMP phosphodiesterase. In this study, site-specific proteolysis and immunoprecipitation were used to map the domain of T alpha that interacts with T beta gamma. We found that Staphylococcus aureus V8 protease rapidly removes a small fragment from T alpha under native conditions, resulting in the formation of a single 38-kDa polypeptide (T alpha'). Under the same conditions, T beta gamma remains intact. A 4.5-fold decrease in the rate of T alpha cleavage by S. aureus protease was observed in the presence of T beta gamma, suggesting T beta gamma binding blocks the protease-sensitive site on T alpha. Amino acid sequence analysis indicated that T alpha' is derived from the cleavage of T alpha at Glu-21. The ability of T alpha' to interact with and activate the retinal phosphodiesterase is not diminished. However, T alpha' is unable to participate in T beta gamma-dependent activities such as the light-stimulated binding of guanine nucleotides, binding to photoexcited rhodopsin, and ADP-ribosylation catalyzed by pertussis toxin. Moreover, the anti-T alpha monoclonal antibody TF16 was able to precipitate T beta gamma in the presence of T alpha, but not with either T alpha' or T alpha-guanosine 5'-O-(3-thiotriphosphate). We conclude that the amino-terminal region of T alpha participates in T beta gamma interaction and discuss our results with respect to the known structure and function of transducin.
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PMID:Characterization of transducin from bovine retinal rod outer segments. Participation of the amino-terminal region of T alpha in subunit interaction. 331 7

Transducin, the guanyl nucleotide-binding regulatory protein of retinal rod outer segments that couples the photon receptor, rhodopsin, with the light-activated cGMP phosphodiesterase, can be resolved into two functional components, T alpha and T beta gamma. T alpha (39 kDa), which is [32P]ADP-ribosylated by pertussis toxin and [32P]NAD in rod outer segments and in purified transducin, was also labeled by the toxin after separation from T beta gamma (36 kDa and approximately 10 kDa); neither component of T beta gamma was a pertussis toxin substrate. Labeling of T alpha was enhanced by T beta gamma and was maximal at approximately 1:1 molar ratio of T alpha : T beta gamma. Limited proteolysis by trypsin of T alpha in the presence of guanyl-5'-yl imidodiphosphate (Gpp(NH)p) resulted in the sequential appearance of proteins of 38 and 32 kDa. The amino terminus of both 38- and 32-kDa proteins was leucine, whereas that of T alpha could not be identified and was assumed to be blocked. The 32-kDa peptide was not a pertussis toxin substrate. Labeling of the 38-kDa protein was poor and was not enhanced by T beta gamma. Trypsin treatment of [32P]ADP-ribosyl-T alpha produced a labeled 37-38-kDa doublet followed by appearance of radioactivity at the dye front. It appears, therefore, that, although the 38-kDa protein was poor toxin substrate, it contained the ADP-ribosylation site. Without rhodopsin, labeling of T alpha (in the presence of T beta gamma) was unaffected by Gpp(NH)p, guanosine 5'-O-(thiotriphosphate) (GTP gamma S), GTP, GDP, and guanosine 5'-O-(thiodiphosphate) (GDP beta S) but was increased by ATP. When photolyzed rhodopsin and T beta gamma were present, Gpp(NH)p and GTP gamma S decreased [32P]ADP-ribosylation by pertussis toxin. Thus, pertussis toxin-catalyzed [32P]ADP-ribosylation of T alpha was affected by nucleotides, rhodopsin and light in addition to T beta gamma. The amino terminus of T alpha, while it does not contain the pertussis toxin ADP-ribosylation site, appeared critical to its reactivity.
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PMID:ADP-ribosylation of transducin by pertussis toxin. 386 17

Dopamine receptors with a pharmacological profile similar to D2 receptors are coenriched with rhodopsin in preparations of bovine retinal membranes. A high density of these receptors are present on photoreceptor membranes. The affinity of the agonist apomorphine for these receptors is decreased by the guanine nucleotides GTP and GppNHp. Treatment of photoreceptor membranes with pertussis or cholera toxin also decreased the affinity of apomorphine and eliminated the effect of GTP.
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PMID:Dopamine receptors on photoreceptor membranes couple to a GTP-binding protein which is sensitive to both pertussis and cholera toxin. 393 12

Hormonal inhibition of adenylate cyclase is mediated by inhibitory receptors and a guanyl nucleotide-binding coupling protein, termed Gi. Similarly, transducin (T), a guanyl nucleotide-binding protein, mediates activation of cGMP phosphodiesterase by the retinal photon receptor, rhodopsin. Gi and T are both heterotrimers consisting of alpha, beta, and gamma subunits; Gi alpha and G beta are similar to T alpha and T beta, respectively. T alpha hydrolyzes GTP in the presence of photolyzed, but not dark, rhodopsin and T beta gamma. Gi alpha and G beta gamma substituted for T alpha and T beta gamma to yield active hybrid complexes, T alpha G beta gamma and Gi alpha T beta gamma. In the absence of T components, rhodopsin-dependent GTPase activity of Gi alpha G beta gamma was observed. Pertussis toxin ADP-ribosylates both T alpha and Gi alpha; ADP-ribosylation of Gi alpha was negligible in the absence of G beta gamma. With G beta gamma, photolyzed, but not dark, rhodopsin unhibited ADP-ribosylation of Gi alpha. In the presence of G beta gamma and photolyzed rhodopsin, GDP and GDP beta S, but not Gpp(NH)p and GTP gamma S, increased the ADP-ribosylation of Gi alpha. The requirements for ADP-ribosylation of Gi alpha by pertussis toxin were similar to those for ADP-ribosylation of T alpha. Rhodopsin appears to interact with Gi in a manner similar to the inhibitory hormone receptors; photolyzed rhodopsin, the active species, corresponds to the agonist-occupied receptor, while dark rhodopsin, the inactive species, can be equated to the free receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Pertussis toxin-catalyzed ADP-ribosylation of adenylate cyclase. Effects of guanyl nucleotides and rhodopsin. 393 69

Cholera toxin and pertussis toxin catalyze ADP-ribosylation of the alpha-subunits of the GTP-binding stimulatory (Ns) and inhibitory (Ni) coupling components, respectively, of adenylate cyclase. Cholera toxin also catalyzes the ADP-ribosylation of transducin, the GTP-binding signal-coupling protein of retinal rod outer segments, and thereby reduces its light-stimulated GTPase activity. We show here that pertussis toxin also ADP-ribosylates transducin. Illumination markedly inhibits the ADP-ribosylation of transducin by pertussis toxin. ADP-ribosylation by this toxin in the dark is also lessened by prior incubation with hydrolysis-resistant GTP analogs. These inhibitory effects indicate that the GDP complex of transducin is the preferred form for ADP-ribosylation by pertussis toxin. Transducin modified by this toxin has a lower affinity for photoexcited rhodopsin than does unmodified transducin. ADP-ribosylation inhibits the light-stimulated GTPase activity of rod outer segments and blocks the signal-coupling activity of transducin in photoactivation of the phosphodiesterase. These and previous results show that cholera and pertussis toxins preferentially ADP-ribosylate the active (GTP-binding) and inactive (GDP-binding) conformations, respectively, of transducin. Correspondingly, ADP-ribosylation by these toxins inhibits GTPase activity by stabilizing transducin in the preferred active (GTP-binding) or inactive (GDP-binding) conformation. The actions of pertussis toxin on retinal rod outer segments provide further evidence for a high degree of homology between retinal transducin and the N proteins of the adenylate cyclase system.
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PMID:ADP-ribosylation of transducin by pertussis toxin blocks the light-stimulated hydrolysis of GTP and cGMP in retinal photoreceptors. 614 83

Our experiments have delineated the flow of information in the cyclic nucleotide cascade of vision of ROS. A single, photoexcited rhodopsin molecule activates several hundred phosphodiesterase molecules in two stages. First, photoexcited rhodopsin (R*) interacts with transducin (T), a peripheral membrane protein consisting of alpha- (39 kD), beta- (36 kD), and gamma- (approximately 10 kD) subunits. R* catalyzes the exchange of GTP for GDP bound to the subunit of transducin. About 500 T alpha- GTPs are produced per photoexcited rhodopsin at low light levels. T alpha-GTP, released from the beta- and gamma-subunits of transducin, then interacts with the phosphodiesterase to relieve the inhibitory constraint imposed by its gamma-subunit. Hydrolysis of GTP bound to T alpha serves to restore the system to the dark state. Transducin is the amplified signal carrier in this light-triggered cascade. The formation of hundreds of T alpha- GTPs is likely to be the first stage of amplification in visual excitation. The photoactivation of the phosphodiesterase in ROS closely resembles the activation of adenylate cyclase in hormone-sensitive cells. Our cholera toxin labeling studies have shown that transducin is akin to the signal-coupling G protein of the adenylate cyclase system. Cholera toxin specifically ADP- ribosylates and inactivates the GTPase activity of T alpha, just as it does with Gs. The action of pertussis toxin on ROS further underscores the homology of the photoreceptor and hormone-responsive systems. It seems likely that transducin, the stimulatory G protein, and the inhibitory G protein are members of the same family of signal-amplifying proteins. The study of the cyclic nucleotide cascade of vision is proving to be rewarding in affording a view of a recurring motif of signal amplification in nature in addition to providing insight into the mechanism of vision.
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PMID:Transducin and the cyclic GMP phosphodiesterase: amplifier proteins in vision. 632 79

Hormonal inhibition of adenylate cyclase is mediated by a guanyl nucleotide binding protein, Gi, which is composed of alpha, beta, and gamma subunits (Gi alpha, G beta gamma). Pertussis toxin blocks hormonal inhibition by catalyzing the ADP-ribosylation of Gi alpha. With purified Gi subunits, but without nucleotides, it was observed that toxin-catalyzed ADP-ribosylation of Gi alpha was negligible in the absence of G beta gamma; ATP, previously shown to increase ADP-ribosylation in membranes, enhanced the ADP-ribosylation of Gi alpha in the absence, more than in the presence, of G beta gamma. Prior studies (Kanaho, Y., Tsai, S.-C., Adamik, R., Hewlett, E.L., Moss, J., and Vaughan, M. (1984) J. Biol. Chem. 259, 7378-7381) had demonstrated that rhodopsin, the retinal photon receptor protein, can replace inhibitory hormone receptors, and stimulate the hydrolysis of GTP by Gi alpha in the presence of G beta gamma. Photolyzed rhodopsin, but not the inactive, dark protein, inhibited ADP-ribosylation of Gi alpha in the presence of G beta gamma. ADP-ribosylation of Gi alpha, in the presence of G beta gamma and photolyzed (but not dark) rhodopsin was increased by guanosine 5'-O-(2-thiodiphosphate) or GDP, but not by (beta, gamma-methylene)guanosine triphosphate or guanosine 5'-O-(3-thiotriphosphate). Presumably, photolyzed rhodopsin and nucleoside triphosphate analogues activate Gi, whereas with dark rhodopsin and nucleoside diphosphates Gi is in the inactive state. The latter appears to be the preferred substrate for pertussis toxin. These observations are consistent with other evidence that rhodopsin and inhibitory hormone receptors are functionally similar.
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PMID:Effects of guanyl nucleotides and rhodopsin on ADP-ribosylation of the inhibitory GTP-binding component of adenylate cyclase by pertussis toxin. 643 19

We examined the functional significance of two residues present in the second (Asp100) and seventh (Asn391) transmembrane domains of the rat cholecystokininB (CCKB) receptor that are highly conserved among the members of the G protein-coupled receptor family. Substitution of Asn for Asp100 by using site-directed mutagenesis did not change the affinity and selectivity for agonists but slightly increased the affinity of three CCKB-selective antagonists of different chemical structures. Cells expressing the mutant receptor exhibited a 50% reduction in CCKB-induced phosphoinositide turnover compared with cells expressing the wild-type receptor, suggesting a critical role for this residue in the coupling of the CCKB receptor to G protein. This latter was shown to be insensitive to pertussis toxin treatment and could therefore belong to the Gq family. Replacement of Asn391 by Asp located in the seventh transmembrane domain did not change agonist binding or phosphoinositide turnover. This suggests that in contrast to the gonadotropin-releasing hormone receptor, there is no direct interaction in the CCKB receptor between Asp100 and Asn391. However, a rhodopsin-based molecular modeling of the CCKB receptor showed a spatial proximity between Asp100 and the carboxyl terminal part of the third intracellular loop, known to interact with G protein. This could explain the reduction in phosphoinositide turnover observed with the Asn100 mutant.
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PMID:Mutation of Asp100 in the second transmembrane domain of the cholecystokinin B receptor increases antagonist binding and reduces signal transduction. 747 7

Triton X-114 phase partitioning, a procedure used for purifying integral membrane proteins, was used to study protein components of the mammalian visual transduction cascade. An integral membrane protein, rhodopsin, and two isoprenylated protein complexes, cyclic GMP phosphodiesterase and Gt beta gamma, partitioned into the detergent-rich phase. Arrestin, a soluble protein, accumulated in the aqueous phase. Gt alpha distributed about equally between phases whether GDP (Gt alpha.GDP) or GTP (Gt alpha.GTP) was bound. Gt beta gamma increased recovery of Gt alpha.GDP but not Gt alpha.GTP in the detergent phase. Trypsin-treated Gt alpha, which lacks the fatty acylated amino-terminal 2-kDa region, accumulated to a greater extent in the aqueous phase than did intact Gt alpha. Trypsinized cGMP phosphodiesterase, which lacks the isoprenyl group, partitioned into the aqueous phase. A carboxyl-terminal truncated mutant (Val-331 stop) of Gt alpha accumulated more in the aqueous phase then did recombinant full-length Gt alpha, supporting the role of the carboxyl terminus in increasing its hydrophobicity. N-Myristoylated recombinant Go alpha was more hydrophobic than recombinant Go alpha without myristate. ADP-ribosylation of Gt alpha catalyzed by NAD:arginine ADP-ribosyltransferase, but not by pertussis toxin, increased hydrophilicity. Triton X-114 phase partitioning can thus semiquantify the hydrophobic nature of proteins and protein domains. It may aid in evaluating changes associated with post-translational protein modification and protein-protein interactions in a defined system.
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PMID:Hydrophobicity and subunit interactions of rod outer segment proteins investigated using Triton X-114 phase partitioning. 762 4

We have previously shown that the S-prenylated cysteine analogue N-acetyl-S-trans,trans-farnesyl-L-cysteine (L-AFC) inhibits basal and formyl peptide receptor-stimulated binding of guanosine 5'-O-(3-thiotriphosphate) (GTP[S]) to and hydrolysis of GTP by membranes of HL-60 granulocytes and have presented evidence suggesting that this inhibition was not caused by reduced protein carboxyl methylation [Scheer, A., & Gierschik, P. (1993) FEBS Lett. 319, 110-114]. We now report a detailed analysis of the structural properties of S-prenylated cysteine analogues required for this inhibition and demonstrate that S-prenylcysteines also suppress basal and receptor-stimulated GTP[S] binding to human peripheral neutrophil and HL-60 granulocyte membranes when stimulated by formyl peptide and complement C5a, respectively. S-Prenylcysteines did not affect pertussis toxin-mediated [32P]ADP-ribosylation of Gi proteins. The inhibitory effect of L-AFC was reversible and was not mimicked by farnesylic acid. L-AFC also interfered with GTP[S] binding to retinal transducin when stimulated by light-activated rhodopsin in a reconstituted system. This inhibitory effect was fully reversed upon increasing the concentration of either the G protein beta gamma dimer or the activated receptor. On the basis of these results, we suggest that S-prenylated cysteine analogues like L-AFC inhibit receptor-mediated G protein activation by specifically and reversibly interfering with the interaction of activated receptors with G proteins, most likely with their beta gamma dimers, rather than by inhibiting alpha.beta gamma heterotrimer formation.
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PMID:S-prenylated cysteine analogues inhibit receptor-mediated G protein activation in native human granulocyte and reconstituted bovine retinal rod outer segment membranes. 771 Oct 17

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