| 3207668 |
Catalysis of a rotational transition in a peptide by crystal forces |
10.1021/bi00419a002. |
Biochemistry |
Catalysis of a rotational transition in a peptide by crystal forces
Abstract
- Detailed examination of the dynamics trajectories of the isolated cyclic peptide cyclo-(Ala-Pro-D-Phe)2 and of the molecule in its crystalline environment led to the unexpected observation that the methyl groups of the alanine residues rotated more frequently during a simulation in the crystal environment than in a simulation of the isolated peptide. In effect, the crystal environment is "catalyzing" the rotational isomerization of the methyl groups. In order to understand how the crystal forces increase the rate of this rotation, and to explore any possible analogy to the inducing of strained conformations of ligands by enzymes, the barriers to rotation in the two environments were studied by using the torsion angle forcing method. The crystal forces induce a different, higher energy, conformation of the peptide than is found for the isolated molecule, and the different rates of rotation have been explained in terms of the resulting specific intramolecular interactions that, it turns out, give rise to the lower rotational barrier. Molecular dynamics simulations of the peptide were also run at higher temperatures in order to calculate the barriers to rotation through the use of Arrhenius plots. The barriers obtained in this way agree well with the barriers obtained through an adiabatic reaction path derived by rotating the methyl through the barrier while minimizing all remaining degrees of freedom. The rates of rotation calculated from these adiabatic barriers also agree well with the rates observed during the 300 K simulations.
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| 3208838 |
Pro-inflammatory effects of bradykinin, sigma-cycloLys1,Gly6bradykinin and sigma-cyclo-kallidin in the rat |
10.1016/0014-2999(88)90159-8. |
Eur J Pharmacol |
Pro-inflammatory effects of bradykinin, sigma-cycloLys1,Gly6bradykinin and sigma-cyclo-kallidin in the rat
Abstract
- A comparison of the effects of bradykinin (BK), sigma-cyclo-BK and sigma-cyclo-kallidin (sigma-cyclo-KD) to induce oedema, hyperalgesia and blood flow in the rat paw was made. BK produced dose-dependent increases in oedema and blood flow and a reduction in the nociceptive pressure threshold. Sigma-Cyclo-BK and sigma-cyclo-KD were more potent than BK at inducing oedema and increasing blood flow but had no effect on nociceptive pressure threshold at the doses used. The relative lack of hyperalgesic activity of sigma-cyclo-BK and sigma-cyclo-KD compared with BK raises the possibility of differences between kinin receptors mediating permeability and blood flow changes and those involved in nociception in this model.
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| 3220657 |
Synthetic amatoxin analogues. II. A proton n.m.r. study of S-deoxo-Ile3-(L)Ala5 and S-deoxo-Ile3-(D)Ala5-amaninamide |
None |
Int J Pept Protein Res |
Synthetic amatoxin analogues. II. A proton n.m.r. study of S-deoxo-Ile3-(L)Ala5 and S-deoxo-Ile3-(D)Ala5-amaninamide
Abstract
- Amatoxin analogues with D and L-Ala substitutions in position 5 have been studied by means of 1- and 2-dimensional n.m.r. spectroscopy at 500 MHz. The assignment of all resonances for both analogues has been carried out mostly with the use of COSY and NOESY type experiments. Temperature coefficients for the amide NH protons have been measured and the data compared to known amatoxin structures. The results obtained demonstrate that the rigidity of the bicyclic amatoxin framework is preserved in the D and L-Ala5 analogues, although the temperature coefficients point to intramolecular hydrogen bonds stronger in the case of the L-Ala analogue. The 10-fold decrease of biological activity is discussed in terms of structural features involving also the Trp4 indole accessibility.
|
| 3242619 |
Identification of the primary structural defect in the dysthrombin thrombin Quick I: substitution of cysteine for arginine-382 |
10.1021/bi00426a013. |
Biochemistry |
Identification of the primary structural defect in the dysthrombin thrombin Quick I: substitution of cysteine for arginine-382
Abstract
- A congenitally dysfunctional form of prothrombin, prothrombin Quick, was isolated from the plasma of an individual with less than 2% of normal prothrombin activity. Following activation of prothrombin Quick, two dysfunctional thrombins, thrombin Quick I and thrombin Quick II, were isolated. Functional characterization of thrombin Quick I indicated an increase in KM and a decrease in kcat, relative to thrombin, for release of fibrinopeptide A. Comparison of kcat/KM for thrombin Quick I to the value obtained for thrombin yielded a relative catalytic efficiency of 0.012 for thrombin Quick I [Henriksen, R. A., & Owen, W. G. (1987) J. Biol. Chem. 262, 4664-4669]. Lysyl endopeptidase digestor of reduced and S-carboxymethylated thrombin and thrombin Quick I has resulted in the identification of an altered peptide in this dysthrombin. Edman degradation of the isolated peptide has shown that the altered residue in this protein is Arg-382 which is replaced by Cys. This could result from a point mutation in the Arg codon, CGC, to yield TGC. Together, these results indicate that Arg-382 is a critical residue in determining the specificity of thrombin toward fibrinogen. Similar relative activities for thrombin Quick I in stimulating platelet aggregation, in the release of prostacyclin from human umbilical vein endothelium, and in the release of fibrinopeptide A suggest that these activities of thrombin share the same specificity determinants.
|
| 3254038 |
Studies of chemical constituents of Manis pentadactyla |
None |
Yao Xue Xue Bao |
Studies of chemical constituents of Manis pentadactyla
Abstract
|
| 3260267 |
Analysis of two cDNA clones encoding the B lymphocyte antigen CD20 (B1, Bp35), a type III integral membrane protein |
10.1084/jem.167.6.1975. |
J Exp Med |
Analysis of two cDNA clones encoding the B lymphocyte antigen CD20 (B1, Bp35), a type III integral membrane protein
Abstract
- Two cDNA clones encoding the pan-B cell CD20 antigen were isolated from a COS cell expression library. The two clones bear identical coding sequences and differ only in the length of the 3' untranslated region. The predicted CD20 sequence is 297 residues long and contains three hydrophobic domains, one of which is long enough to span the membrane twice. COS cells transfected with either CD20 clone express an immunoreactive protein of 33 kD.
|
| 3261799 |
Synthesis, conformation, and immunosuppressive activity of a conformationally restricted cyclosporine lactam analogue |
10.1021/jm00117a022. |
J Med Chem |
Synthesis, conformation, and immunosuppressive activity of a conformationally restricted cyclosporine lactam analogue
Abstract
- Cyclosporine A (CsA, 1), an immunosuppressive cyclic undecapeptide, in apolar solvents adopts a II' beta-turn at the Sar3-MeLeu4 residues. D-Proline3Cs has been reported to be a nonimmunosuppressive analogue in which the II' beta-turn is retained. In order to determine if this loss of activity is caused by steric hindrance between the Cs analogue and its receptor or is caused by a change in the peptide conformation, an analogue that stabilizes a II' beta-turn has been synthesized, lactam3,4Cs. We also have studied the solution conformation of two other analogues, D-MeAla3Cs and L-MeAla3Cs. The conformations have been established by 1D difference NOE and 2D (NOESY or ROESY) NMR. The conformations of lactam3,4Cs and D-MeAla3Cs are indistinguishable from that of CsA in solution. L-MeAla3Cs was found to adopt a conformation with a cis amide bond between Sar3 and MeLeu4. The inhibition of concanavalin A stimulated thymocytes by CsA, D-MeAla3Cs, L-MeAla3Cs, and lactam3,4Cs gave IC50 values (nM) of 5, 6, 100, and 100, respectively. The weak immunosuppressive activity of lactam3,4Cs possessing the II' beta-turn suggests that the loss of activity for 4 is due to steric hindrance with the Cs receptor."
|
| 3283938 |
Insulin-resistant diabetes due to a point mutation that prevents insulin proreceptor processing |
10.1126/science.3283938. |
Science |
Insulin-resistant diabetes due to a point mutation that prevents insulin proreceptor processing
Abstract
- A point mutation in the human insulin receptor gene in a patient with type A insulin resistance alters the amino acid sequence within the tetrabasic processing site of the proreceptor molecule from Arg-Lys-Arg-Arg to Arg-Lys-Arg-Ser. Epstein-Barr virus-transformed lymphocytes from this patient synthesize an insulin receptor precursor that is normally glycosylated and inserted into the plasma membrane but is not cleaved to mature alpha and beta subunits. Insulin binding to these cells is severely reduced but can be increased about fivefold by gentle treatment with trypsin, accompanied by the appearance of normal alpha subunits. These results indicate that proteolysis of the proreceptor is necessary for its normal full insulin-binding sensitivity and signal-transducing activity and that a cellular protease that is more stringent in its specificity than trypsin is required to process the receptor precursor.
|
| 3290210 |
Structure and bactericidal activity of an antibiotic dodecapeptide purified from bovine neutrophils |
None |
J Biol Chem |
Structure and bactericidal activity of an antibiotic dodecapeptide purified from bovine neutrophils
Abstract
- Cytoplasmic granules of neutrophils store a variety of cationic polypeptides, which exert in vitro a potent antibacterial action and are potentially involved in host defense mechanisms. From an acid extract of bovine neutrophil granules we have purified over 2,000-fold a dodecapeptide exhibiting bactericidal activity against both Escherichia coli and Staphylococcus aureus at 10(-7)-10(-5) M concentration. The purification procedure involved only two steps of ion-exchange and reversed-phase chromatography. The peptide, named bactenecin, has the amino acid sequence, Arg-Leu-Cys-Arg-Ile-Val-Val-Ile-Arg-Val-Cys-Arg, maintained in a cyclic structure by a disulfide bond between the two cysteine residues. Computer modeling of the dodecapeptide resulted in a conformation in which the chain adopts an antiparallel extended structure forming a gamma turn at residue 7.
|
| 3301821 |
fhuC and fhuD genes for iron (III)-ferrichrome transport into Escherichia coli K-12. |
10.1128/jb.169.8.3844-3849.1987 |
J. Bacteriol. |
fhuC and fhuD genes for iron (III)-ferrichrome transport into Escherichia coli K-12.
Abstract
- The nucleotide sequence for a 1,900-base-pair region of the Escherichia coli chromosome that includes the genes fhuC and fhuD was determined. Within this sequence are two open reading frames: nucleotides 127 to 921 and nucleotides 924 to 1811. These coding regions specify a FhuC protein with an Mr of 28,423 and a mature FhuD protein with an Mr of 29,610. The deduced amino acid sequence of FhuC shows extensive homology with those of components of some bacterial transport systems which are peripheral proteins of the cytoplasmic membrane. Because the FhuD protein contains a typical signal sequence of 30 amino acids at the amino terminus and displays characteristics of a soluble protein, it may be exported into the periplasm.
|
| 3329716 |
The human EGF receptor gene: structure of the 110 kb locus and identification of sequences regulating its transcription. |
10.1016/0006-291x(84)90926-4 |
Oncogene Res. |
The human EGF receptor gene: structure of the 110 kb locus and identification of sequences regulating its transcription.
Abstract
- The human epidermal growth factor receptor (EGFR) proto-oncogene is shown to span 110 kb of DNA divided into 26 exons. Analysis of sequences surrounding exon 1 reveals a highly CG rich region which promotes transcription. The activity of the EGF receptor promoter can be modulated by E1A protein and receptor RNA levels increased by stimulation with phorbol ester or fetal calf serum. Promoter activity is assayed by linkage to the chloramphenicol acetyl transferase gene and transfection in three cell lines, with quantitation of plasmid DNA uptake by isolation of a Hirt supernatent from each transfection. Deletion analysis of the CG rich promoter region of the gene and construction of chimeric EGFR/SV40 promoters are used to demonstrate positive transcription elements located both within exon 1 and 5' to the start of transcription. Negative regulation of transcription by sequences within a -140 to +80 region is suggested. Cotransfection experiments suggest a requirement for the interaction of DNA binding protein Sp1 for maximal activity. Finally, derepression of a positive regulatory sequence located in exon 1 during cotransfection experiments is shown.
Results are discussed in reference to the multilevel regulation of EGF receptor expression.
|
| 3337272 |
Verapamil blockade of pressor and uterine responses to AVP-OT analogue, oxypressin |
10.1152/ajpregu.1988.254.1.R75. |
Am J Physiol |
Verapamil blockade of pressor and uterine responses to AVP-OT analogue, oxypressin
Abstract
- The effects of the calcium channel blocker verapamil on simultaneously recorded uterine and pressor responses to the equipotent (in eliciting these responses) oxytocin-vasopressin analogue, oxypressin, were studied in urethan-anesthetized and pentolinium- and indomethacin-treated rats during injections and infusions of this analogue. Doses of verapamil that almost completely blocked the pressor response to infused oxypressin had no effect on a pressor response to injected oxypressin of equal magnitude. Larger doses of verapamil blocked the pressor response to injected oxypressin somewhat. Uterine responses were only marginally affected by these doses of verapamil, and there was no significant difference between infusion and injection or between estrus and diestrus.
|
| 3420141 |
Constrictory activity of three new arginine-vasopressin (AVP) analogues (Ala-AVP, Ser-Ala-AVP, Thr-Ser-Ala-AVP) towards isolated rat tail artery as related to AVP alone |
10.1016/s0031-6989(88)80013-4. |
Pharmacol Res Commun |
Constrictory activity of three new arginine-vasopressin (AVP) analogues (Ala-AVP, Ser-Ala-AVP, Thr-Ser-Ala-AVP) towards isolated rat tail artery as related to AVP alone
Abstract
- The constrictory activity of vasopressin and its three novel analogues extended by 1-3 amino acids in accordance with the sequence of the bovine arginine-vasopressin neurophysin II precursor has been studied on isolated rat tail artery preparation. The analogues showed lower constrictory potency than AVP, but these agents strongly interacted with AVP. The net effect of interactions appeared complex and dependent on the nature and concentrations of the interacting agents. Basing on recent findings (Land et al. 1982) concerning the sequence of the bovine arginine-vasopressin neurophysin II precursor, Lammek et al. (1987) synthesized vasopressin analogues with primary structures derived from this precursor. Three such analogues, Ala-AVP, Ser-Ala-AVP, and Thr-Ser-Ala-AVP, showed pressor activity (147, 109, and 86 international units/mumol respectively) and antidiuretic activity (52, 130, and 48 international units/mumol, respectively) after intravenous administration to rats (Lammek et al. 1987). Having in view the possible clinical applications of vasopressin analogues and hormonogens in the treatment of bleeding disorders we were interested in the direct effect of the agents on isolated blood vessels. As the analogues considered may theoretically appear in a living system and interact with the native AVP, such interaction on the isolated rat tail artery preparation was analysed.
|
| 3435104 |
Dosage, timing, and route of administration of cyclosporin A and nonimmunosuppressive derivatives of dihydrocyclosporin A and cyclosporin C against Schistosoma mansoni in vivo and in vitro |
10.1128/AAC.31.10.1567. |
Antimicrob Agents Chemother |
Dosage, timing, and route of administration of cyclosporin A and nonimmunosuppressive derivatives of dihydrocyclosporin A and cyclosporin C against Schistosoma mansoni in vivo and in vitro
Abstract
- The prophylactic and therapeutic effects of cyclosporin A (CsA) against percutaneous Schistosoma mansoni infection in MF1 mice were dose related and dependent on the temporal relationship between drug administration and infection. Antischistosomal activity, assessed by worm recovery from the host 6 weeks after infection, was most effective (complete worm elimination) when CsA was administered at the time of infection. Oral administration of CsA was less effective than subcutaneous injection, and no prophylactic activity was demonstrated by the former route. Derivatives of dihydrocyclosporin A and cyclosporin C, which have been reported to exert only poor immunosuppressive activity, exhibited efficacy against S. mansoni similar to that of CsA and were also less effective when given orally. Subcutaneous, but not oral CsA reduced cercarial skin penetration and transformation success; the derivative of dihydrocyclosporin A, however, was without effect. Moreover, CsA, but not the derivative of dihydrocyclosporin A, reduced the number of worms established after intraperitoneal injection of cercariae. These data provide further insight into the antischistosomal activity of cyclosporins, which appears to be distinct from their immunomodulatory properties, since parasite killing was retained both in immunologically disparate mice and with poorly immunosuppressive cyclosporin derivatives.
|
| 3447155 |
Partial amino acid sequence analyses of human placental insulin receptor. |
10.1126/science.2544997 |
Protein Seq. Data Anal. |
Partial amino acid sequence analyses of human placental insulin receptor.
Abstract
- Tryptic peptides were isolated from human insulin receptor (1.8 nmol) by sequential reverse-phase HPLC on SynChropak RP-C8 and Vydac C-18. Nearly 20 peptides were analyzed for amino acid composition, which revealed that the yield of tryptic peptides averaged 300 pmol. By gas-phase microsequencing five peptides were sequenced. N-acetylglucosamine was found in two peptides. These data are compared with the amino acid sequence of the insulin receptor deduced from cloned cDNA encoding for human insulin receptor.
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