Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0033036 (APC)
 10,214 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To assess the potential role of the lipoxygenase (LO) pathway in the vasculature in an angiotensin II (ANG II)-dependent model of hypertension, we investigated the effect of LO pathway inhibition on blood pressure in the two-kidney, one-clip (2K,1C) Goldblatt hypertensive rat. The development of renovascular hypertension in 2K,1C rats was attenuated by oral administration of phenidone (Phe, 60 mg.kg-1.day-1), a nonselective LO inhibitor, throughout the 3 wk of observation after renal artery constriction. In contrast, the same treatment protocol had no effect on the evolution of hypertension in the deoxycorticosterone acetate-salt rat, which is considered to be an ANG II-independent form of hypertension. The hypotensive effect of Phe was not associated with changes in plasma renin or aldosterone concentration (PRC and PAC, respectively). In vitro synthesis of 12-hydroxyeicosatetraenoic acid (12-HETE) by aortic segments was increased in 2K,1C hypertensive rats compared with sham-operated rats. In addition, the synthesis of 12-HETE was suppressed by the in vitro addition of Phe (10(-4) M) to aortic-segment incubates obtained from 2K,1C rats and sham-operated rats. Acute administration of Phe (30 or 60 mg/kg) in 2K,1C hypertensive rats produced a rapid and sustained decrease in mean blood pressure (MBP). This decrease in MBP was accompanied by a brisk rise in PRC and PAC. In contrast, bolus administration of indomethacin, a selective cyclooxygenase inhibitor, did not affect MBP, PRC, or PAC.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Inhibition of lipoxygenase pathway reduces blood pressure in renovascular hypertensive rats. 212 26

Rabbit polyclonal antibodies to a synthetic peptide, NH2-Asp-Thr-Asn-Gln-Val-Asp-Gln-Lys-Asp-Gln-Leu-Asp-Phe-Arg-CONH2 (A Pep), have been produced. This sequence is identical to that contained in the tetradecapeptide released from bovine protein C (PC) as a result of its conversion to its activated form (APC), except that Phe13 replaced the normal Pro13, in order to discourage cross-reactivity of antibodies to the carboxylterminal portion of APep with PC. The antibody pool obtained reacted with PC and showed virtually no cross-reactivity toward either APC or several typical plasma proteins. This general approach should serve well as a means of production of antibodies with a designed specificity capable of distinguishing between forms of the same protein that arise by release of peptide material.
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PMID:Generation of an antibody with a designed specificity difference for protein C and activated protein C. 280 12

To identify a site within the insulin receptor ectodomain which forms a binding pocket for B25 Phe and is responsible for initiating conformational changes required for high affinity binding of insulin we have used a novel photoreactive insulin, despentapeptide-(B26-B30) [B25 p-azidophenylalanine-alpha-carboxamide] insulin (APC insulin). This derivative has a highly photoreactive azido group incorporated into the aromatic ring of the B25 phenylalanine amide. APC insulin bound to human insulin receptors overexpressed on a transfected Chinese hamster ovary cell line (P3-A) with an apparent potency of 9-fold relative to that of native insulin and stimulated lipogenesis in rat adipocytes with an average potency equal to porcine insulin. Addition of biotin to the B1 Phe amino group to form despentapeptide-(B26-B30) [B1 (6-biotinylamidocaproyl)phenylalanine B25 p-azidophenylalanine-alpha-carboxamide] insulin derivative (Bio-APC insulin) did not adversely affect receptor-binding affinity and provided a convenient ligand for purification of cross-linked complexes. The efficiency of receptor cross-linking with these reagents was high (70%). To identify the site(s) of cross-linking, the insulin receptor in P3-A cells was first metabolically labeled with various individual 3H-labeled amino acids and then photoaffinity labeled with 125I-Bio-APC insulin, isolated, and digested with Lys-C endoproteinase. The resulting cross-linked peptide fragments were separated by streptavidin-affinity chromatography and sequenced. The smallest identified fragment comprised residues 704-718 of the COOH terminus of the alpha-subunit of the insulin receptor. This B25 Phe cross-linked region of the alpha-subunit lies just upstream of the Exon 11-encoded 12-amino acid COOH-terminal region. Aromatic residues in this predicted alpha-helical region may form a binding pocket for B25 Phe to initiate conformational changes required for stabilizing the high affinity binding state.
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PMID:Cross-linking of a B25 azidophenylalanine insulin derivative to the carboxyl-terminal region of the alpha-subunit of the insulin receptor. Identification of a new insulin-binding domain in the insulin receptor. 796 85

Residues 46 and 54 on pigeon cytochrome c 43-58 (p43-58) analogues function as agretopes (sites bound to MHC molecules). Phenylalanine (F) and alanine (A) at positions 46 and 54 on p43-58 respectively bind to I-Ab. Aspartic acid (D) and alanine at positions 46 and 54 respectively bind to I-Ak. To determine the allele specific binding sites (desetope (s)) on class II molecules that are correspondent to the agretopes of peptide antigen (Ag), we analyzed directly binding capacity of p43-58 analogues with glutamic acid (E) at the epitopic position 50 (50E) to L cell transfectants expressing recombinant I-A molecules between b and k types. An Ak binding peptide, 46D50E54A, bound to transfectant possessing amino acid sequence of k type on N-terminal half of alpha-helix of A alpha-chain irrespective of the b type sequence on the other part, whereas an Ab binding peptide, 46F50E54A, did not bind to these transfects. Thus, agretopic residue 46 of 46D50E54A peptides appeared to bind to N-terminal half of alpha-helix of A alpha-chain. To define critical residues for the allele specific peptide binding, we then analyzed peptide binding capacity of Ak mutants substituted one of four polymorphic residues between Ak and Ab molecules. An Ak mutant, Ak alpha(56A), where arginine (R) at position 56 of the Ak alpha-chains was substituted with alanine located at the same position 56 of the Ab alpha-chains hardly bound 46D50E54A. By contrast, the Ak alpha(56A) bound 46F50E54A. Furthermore, Ak restricted T cell hybridomas responded to 46F50E54A but not to 46D50E54A in the presence of the Ak alpha(56A) APC. Thus, an amino acid on the position 56 of A alpha-chain determines critically specificity of the allele specific peptide binding (desetope).
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PMID:[Analysis of the allele specific Ag-binding site on murine class II MHC]. 864 75

The identity and abundance of self-peptide/MHC class I complexes that serve as ligands for alloreactive T cells remain largely unknown. Using the Kb-restricted, alloreactive T cells as a probe, the Ag precursor gene, adenosine phosphoribosyl transferase (APRT), was isolated by expression cloning. Its naturally processed product was identified as the SLVELTSL (SEL8) octapeptide. The SEL8 peptide shared five residues with the previously identified SVVEFSSL (JAL8) peptide that stimulated the same T cell, but lacked the critical phenylalanine/tyrosine residue at the primary p5 anchor position. Despite the absence of this key conserved anchor residue, SEL8 was bound tightly by Kb MHC and yet was expressed at less than 10 copies/cell. Mutations in the donor APRT gene in the APC caused a concomitant loss in the ability of APCs to stimulate T cells. The results confirm that the display of peptide/MHC complexes in cells exceeds the predictions based upon consensus motifs, and that CD8+ alloreactive and conventional Ag-specific T cells are indistinguishable in their ability to recognize unique and rare peptide/MHC class I complexes.
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PMID:Alloreactive CD8+ T cells can recognize unusual, rare, and unique processed peptide/MHC complexes. 890 23

PAC spectra (perturbed angular correlation of gamma-rays) of cadmium-substituted carboxypeptidase A (CPD) show that the enzyme in solution imposes a flexible, pH- and chloride-dependent coordination structure on the metal site, in contrast to what is found in the crystalline state. A much more restricted coordination geometry occurs for the steady-state peptide intermediates of Bz-Gly-l-Phe and Bz-Gly-Gly-l-Phe in solution, suggesting that substrate binding locks the structure in a rigid conformation. The results further indicate that the peptide intermediate has a six-coordinated metal coordination geometry with an OH- ligand at the solvent site and a carbonyl oxygen at an additional ligand site. In marked contrast, conformational rigidity is not induced by the inhibitor/poor substrate Gly-L-Tyr nor by the products of high turnover substrates, Bz-Gly, Bz-Gly-Gly, and L-Phe. These results are consistent with an intact scissile peptide bond in the enzyme-substrate complex of Bz-Gly-L-Phe and Bz-Gly-Gly-L-Phe. A single nuclear quadrupole interaction (NQI) is observed for the crystalline state of the enzyme between pH 5.7 and pH 9.4. This NQI agrees with calculations based on the metal coordination geometry for cadmium in crystalline CPD derived from X-ray diffraction studies. A single broad distribution of NQIs is observed for CPD in sucrose solutions and 0.1 M NaCl at pH values below 6.5. This NQI (NQI-1') has parameters very close to those for the crystalline state. The enzyme metal site, characterized by this NQI, is converted into two new enzyme metal sites over the pH range of 6.5-8.3. The metal coordination sphere of one of these has a NQI (NQI-1) with parameters similar to those at lower pH values (NQI-1') while the other NQI (NQI-2) is characterized by markedly different NQI parameters. Angular overlap model (AOM) calculations indicate that the coordination sites giving NQI-1' and NQI-1 both have a metal-bound water molecule while the coordination site giving NQI-2 has a metal-bound hydroxide ion. PAC results at pH 8.3-10.5 indicate that in this pH range the two metal coordination geometries related to NQI-1 and NQI-2 occur in a pH independent ratio of 2:1, with the one with the water ligand being the most abundant species. The observed pH-independent equilibrium between the two different metal coordination geometries for cadmium can be explained by an equilibrium between tautomeric forms of a hydrogen bond between the Glu-270 carboxyl group and the metal-bound water (Glu-270 COO-...(HOH)M <==> Glu-270 COOH...(OH-)M) being slow on the time scale of a PAC experiment, i.e., slower than 0.5 micros. We finally suggest that NQI-1' observed at low pH reflects an enzyme species containing a metal-coordinated water molecule and the protonated carboxyl group of Glu-270.
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PMID:Structure and dynamics of the metal site of cadmium-substituted carboxypeptidase A in solution and crystalline states and under steady-state peptide hydrolysis. 929 72

The glycopeptide hormone catfish somatostatin (somatostatin-22) has the amino acid sequence H-Asp-Asn-Thr-Val-Thr-Ser-Lys-Pro-Leu-Asn-Cys-Met-Asn-Tyr-Phe-Trp-Lys-Se r-Arg-Thr-Ala-Cys-OH; it includes a cyclic disulfide connecting the two Cys residues, and the major naturally occurring glycoform contains D-GalNAc and D-Gal O-glycosidically linked to Thr5. The linear sequence was assembled smoothly starting with an Fmoc-Cys(Trt)-PAC-PEG-PS support, using stepwise Fmoc solid-phase chemistry. In addition to the nonglycosylated peptide, two glycosylated forms of somatostatin-22 were accessed by incorporating as building blocks, respectively, Nalpha-Fmoc-Thr(Ac3-alpha-D-GalNAc)-OH and Nalpha-Fmoc-Thr(Ac4-beta-D-Gal-(1-->3)-Ac2-alpha-D-GalNAc)-O H. Acidolytic deprotection/cleavage of these peptidyl-resins with trifluoroacetic acid/scavenger cocktails gave the corresponding acetyl-protected glycopeptides with free sulfhydryl functions. Deacetylation, by methanolysis in the presence of catalytic sodium methoxide, was followed by mild oxidation at pH 7, mediated by Nalpha-dithiasuccinoyl (Dts)-glycine, to provide the desired monomeric cyclic disulfides. The purified peptides were tested for binding affinities to a panel of cloned human somatostatin receptor subtypes; in several cases, presence of the disaccharide moiety resulted in 2-fold tighter binding.
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PMID:Chemical synthesis and receptor binding of catfish somatostatin: a disulfide-bridged beta-D-Galp-(1-->3)-alpha-D-GalpNAc O-glycopeptide. 1066 64

The aim of the present study was to investigate whether the overall oxidation state of plasma proteins is associated with changes of circulating pro- and anticoagulant markers in healthy subjects (n = 99, 49 males, 50 females, aged from 6 to 91 yrs.). The carbonyl content of plasma proteins was measured and validated as an ex vivo index of the overall protein oxidation state due to its correlation with the plasma level of o-tyrosine (r = 0.87, P <0.0001), which is a well known oxidized product of L-phenylalanine. Using a multivariate analysis the carbonyl content of plasma protein was positively associated with procoagulant markers such as prothrombin F1 + 2 (r = 0.28, P = 0.0019) and fibrinopeptide A, (FpA) (r = 0.278, P = 0.003), as well as with the soluble derivative of the endothelial protein thrombomodulin (TM) (r = 0.469, P <0.0001). The procoagulant marker of thrombin activity, FpA, was significantly and positively correlated with the anticoagulant product of thrombin, namely the Protein C activation peptide (PCP), only in the tertile with low protein carbonyl content. At higher tertiles this correlation was no longer observed, thus suggesting a detrimental effect of oxidative stress on the TM/Protein C anticoagulant pathway. In 15 subjects with high carbonyl content of plasma protein, treatment for 18 days with 600 mg/d of vitamin E did not substantially modify the protein carbonyl content, the anticoagulant markers APC/PCP, and all procoagulant markers except F1+2, whose value significantly decreased by 25%. In conclusion, the present study shows that a high plasma protein oxidation ex vivo is associated with an overall hemostatic imbalance, which favors procoagulant markers. Vitamin E treatment in vivo restores only in part the equilibrium between pro- and anticoagulant pathways. This may open the way to further studies aimed at elucidating the mechanisms by which the oxidative stress is linked to activation of the coagulation system in atherothrombotic disorders.
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PMID:Plasma protein oxidation is associated with an increase of procoagulant markers causing an imbalance between pro- and anticoagulant pathways in healthy subjects. 1184 57

VIP and pituitary adenylate cyclase-activating polypeptide (PACAP) are two regulatory peptides that possess remarkable amino acid sequence homology and act through common receptors, named PAC(1), VPAC(1), and VPAC(2). PAC(1) receptor is selective for PACAP, whereas VPAC(1) and VPAC(2) receptors bind both VIP and PACAP. We have investigated the expression and function of VIP, PACAP, and their receptors in the zona glomerulosa (ZG), zonae fasciculata and reticularis, and adrenal medulla (AM) of the human adrenal cortex. RT-PCR and RIA detected VIP and PACAP expression exclusively in AM cells. RT-PCR demonstrated the presence of PAC(1) mRNA only in AM and of VPAC(1) and VPAC(2) mRNAs in both ZG and AM cells. VIP and PACAP concentration-dependently increased aldosterone and catecholamine secretion from cultured ZG and AM cells. The catecholamine response to both peptides was higher than the aldosterone response, and the secretagogue action of PACAP was more intense than that of VIP. The aldosterone response of cultured ZG cells to VIP or PACAP was unaffected by the PAC(1) receptor antagonist PACAP-(6-38) (PAC(1)-A), but was significantly decreased by the VPAC(1) receptor antagonist [Ac-His(1),D-Phe(2),Lys(15),Arg(16)]VIP-(3-7),GH-releasing factor-(8-27)-NH(2) (VPAC(1)-A). The catecholamine response of cultured AM cells to VIP was lowered by VPAC(1)-A and unaffected by PAC(1)-A; conversely, the catecholamine response to PACAP was reduced by both PAC(1)-A and VPAC(1)-A. Simultaneous exposure to both antagonists did not abolish the catecholamine response to PACAP. Collectively, our findings allow us to conclude that in human adrenals 1) VIP and PACAP biosynthesis exclusively occurs in AM cells; 2) ZG cells are provided with functional VPAC(1) and VPAC(2) receptors, whose activation by VIP or PACAP elicits a moderate aldosterone response; 3) AM cells possess PAC(1), VPAC(1), and VPAC(2) receptors, whose activation evokes a marked catecholamine response; and 4) the catecholamine response to PACAP is more intense than that to VIP, because it is mediated by all subtypes of VIP/PACAP receptors.
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PMID:Expression and function of vasoactive intestinal peptide, pituitary adenylate cyclase-activating polypeptide, and their receptors in the human adrenal gland. 1205 Feb 16

We developed previously VPAC(1) [vasoactive intestinal peptide (VIP)/pituitary adenylate cyclase-activating peptide (PACAP) receptor]>VPAC(2) receptor selective ligands. Replacement of the VIP-Thr(11) by an Arg(11) in these ligands contributed to their selectivity: Arg(11)-VIP had a 200-fold lower affinity when compared with VIP at VPAC(2) receptors as opposed to 3- to 5-fold higher affinity at VPAC(1) receptors. Comparison of the binding and functional properties of related VIP analogues suggested that the VPAC(1) selectivity of Arg(11)-VIP was due to the loss of a hydrogen bond between the hydroxy group of Thr residue and the VPAC(2) receptor, steric hindrance between the Arg side chain and the VPAC(2) receptor and charge attraction by the VPAC(1) receptor. Comparison of the ability of VIP analogues to activate adenylate cyclase through chimaeric VPAC(1)/VPAC(2) and VPAC(2)/VPAC(1) receptors indicated that the first extracellular receptor loop carried most of the VPAC(2) receptors' ability to discriminate VIP from Arg(11)-VIP. Based on results obtained for a truncated VPAC(2) receptor and the closely related PACAP-preferring receptor (PAC(1)) and secretin receptors, we hypothesized that Thr(11) interacted with the VPAC(2) receptor Tyr(184) (similar to the VPAC(1) receptor Phe(200) residue). The Y184F (Tyr(184)-->Phe) VPAC(2) mutant lost the ability to discriminate VIP from Val(11)-VIP, and the F200Y VPAC(1) mutant acquired the ability to discriminate the natural peptide from Val(11)-VIP. These results support the hypothesis that the hydroxy group of the native VIP-Thr(11) side chain can indeed form a hydrogen bond with the Tyr side chain in the VPAC(2) receptor.
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PMID:Evidence for a direct interaction between the Thr11 residue of vasoactive intestinal polypeptide and Tyr184 located in the first extracellular loop of the VPAC2 receptor. 1247 94


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