摘要:

AbstractLipidation with long‐chain di‐fattyacyl‐glycerol moieties was used to anchor gastrin and CCK peptides irreversibly to lipid bilayers. Intervesicular lipopeptide transfer to model phospholipid bilayers is fast and quantitative, leading to a different mode of insertion of lipo‐gastrin and lipo‐CCK in lipid bilayers. Lipo‐gastrin remains exposed to the bulk solvent in a predominantly random coil structure as a consequence of electrostatic repulsion, whereas lipo‐CCK exhibits a pronounced tendency to form peptide domains with insertion of its C‐terminus into more hydrophobic compartments of the bilayer. Thereby Ca2+at physiological concentrations favours this aggregational phenomenon. Since both lipo‐peptides were found to retain almost full receptor affinity despite their irreversible anchorage to the bilayer, a membrane‐bound pathway in the receptor recognition and binding process is indeed possible. According to the data collected in this study, CCK might possibly use this pathway, whereas accumulation of gastrin on the cell membrane with prefolding of the ligand at the water/lipid interface is hardly conceivable. Nevertheless the observed receptor interaction of the deliberately membrane‐anchored gastrin offers interesting constraints for computational docking experiments on a modelled CCK‐B/gastrin receptor by additionally taking into account information derived from mutagenesis studies. Despite the limitations of such modelling experiments, the resulting picture of the gastrin/receptor complex allowed the visualization and rationalization of the experimental results of the extensive structure–function studies performed previously on this family of gastrointestinal hormones. © 1997 European Peptide Societ

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199701)3:1<1::AID-PSC85>3.0.CO;2-L

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractA series of peptides patterned on the principal neutralizing domain of the HIV‐1 envelope glycoprotein gp120 have been synthesized by solid‐phase techniques. Interestingly,in vitroexperiments have shown that some of these peptides specifically interact with CD4 and, in particular, that the peptide corresponding to the sequence 307–330 of the HIV‐1 MN isolate was able to enhance infection in a dose‐ specific and not a strain‐restricted way. To bypass problems observed in preliminary runs, several peptides were synthesized by both Fmoc and Boc chemistry. Comparison of the two strategies has allowed the set up of convenient protocols for the preparation of the target peptides in good yield, and with the high‐purity grade needed for biological and physicochemical studies. Since the biological effects were present in the carboxyl‐free C‐terminal linear peptide but not in the amidated C‐terminal analogue, preliminary conformational studies by circular dichroism and nuclear magnetic resonance techniques were also performed in an attempt to correlate these effects with possible contributions of structured conformations as predicted by theoretical calculations. The possibility of a β‐turn structure for the crucial Gly‐Pro‐Gly‐Arg sequence has been confirmed by 2D NMR experiments. Ongoing studies suggest the exploitation of the activating properties of the MN‐derived peptides to design a more sensitive and innovative serological test based on the virus itself and not on anti‐HIV antibodies, as is the case for the large majority of tests currently in use. © 1997 European Peptide

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199701)3:1<15::AID-PSC81>3.0.CO;2-2

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractWe report the solid‐phase synthesis and some pharmacological properties of 12 position three modified analogues (peptides 1–12) of the potent non‐selective antagonist of the antidiuretic (V2‐receptor), vasopressor (V1a‐receptor) responses to arginine vasopressin (AVP) and of the uterine contracting (OT‐receptor) responses to oxytocin (OT), [1(‐β mercapto‐β,β‐pentamethy lenepropionic acid)‐2‐O‐ethyl‐d‐tyrosine 4‐valine] arginine vasopressin [d(CH2)5D‐Tyr(Et)2VAVP] (A) and two analogues of (B) (peptides 13,14), the 1,2,3,4‐tetrahydroisoquinoline‐3‐carboxylic acid3(Tic3) analogue of (A). Peptides 1–12 have the following substituents at position three in (A): (1) Pro; (2) Oic; (3) Atc; (4)D‐Atc; (5) Aic; (6)D‐Phe; (7) Ile; (8) Leu; (9) Tyr; (10) Trp; (11) Hphe; (12) [HO]Tic; Peptide (13) is the Tyr‐NH29analogue of (B): Peptide (14) is theD‐Cys6analogue of (B). All 14 new peptides were evaluated for agonistic and antagonistic activities inin vivoV2and V1aassays and inin vitro(no Mg2+)noxytocic assays. With the exception of theD‐Phe3peptide (No. 6), which exhibits very weak V2agonism (…0.0017 u/mg), none of the remaining 13 peptides exhibit any agonistic activities in these assays. In striking contrast to their deleterious effects on agonistic activities in AVP, the Pro3, Oic3, Tyr3, Trp3and Hphe3substitutions in (A) are very well tolerated, leading to excellent retention of V2, V1aand OT antagonistic potencies. All are more potent as V2antagonists than the Ile3and Leu3analogues of (A). The Tyr‐NH29andD‐Cys6substitutions in (B) are also well tolerated. The anti‐V2pA2values of peptides 1–5 and 7–14 are as follows (1) 7.77±0.03; (2) 7.41± 0.05; (3) 6.86±0.02; (4) 5.66±0.09; (5) …5.2; (7) 7.25± 0.08; (8) 6.82±0.06; (9) 7.58±0.05; (10) 7.61±0.08; (11) 7.59±0.07; (12) 7.20±0.05; (13) 7.57±0.1; (14) 7.52± 0.06. All analogues antagonize the vasopressor responses to AVP, with anti‐V1apA2values ranging from 5.62 to 7.64, and thein vitroresponses to OT, with anti‐OT pA2values ranging from 5.79 to 7.94. With an anti‐V2potency of 7.77±0.03, the Pro3analogue of (A) is surprisingly equipotent with (A), (anti‐V2pA2=7.81±0.07). These findings clearly indicate that position three in AVP V2/V1aantagonists, in contrast to position three in AVP agonists, is much more amenable to structural modification than had heretofore been anticipated. Furthermore, the surprising retention of V2antagonism exhibited by the Pro3, Oic3, Tyr3, Trp3and Hphe3analogues of (A), together with the excellent retention of V2antagonism by the Tyr‐NH29andD‐Cys6analogues of (B) are promising new leads to the design of potent and possibly orally active V2antagonists for use as pharmacological tools and/or as radioiodinatable ligands and for development as potential therapeutic agents for the treatment of the hyponatremia caused by the syndrome of the inappropriate secretion

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199701)3:1<31::AID-PSC82>3.0.CO;2-Y

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractA 17‐mer sequence was selected as a model to study the influence of modifications of terminal ends both on the conformation of a peptide and on its antigenicity towards naturally developing antibodies. This sequence corresponded to a tandemly repeated motif, found in a long repetitive region, with high helical propensity, of aPlasmodium falciparumliver‐stage antigen (LSA‐1), immunogenic in man. Our model peptide was synthesized with ionizable or non‐ionizable ends, or modified in both extremities by introduction of the helix‐promoting residue α‐aminoisobutyric acid (Aib). Helical contribution, absent in the 17 amino‐acid sequence possessing ionizable ends, was detectable when non‐ionizable ends were introduced, and dramatically increased in the Aib‐modified analogue. The presence of ionizable ends totally abolished reactivity towards human sera, otherwise detectable with the peptide possessing non‐ionizable ends. While modification by Aib residues was neither detrimental nor beneficial to antigenicity in solution, it clearly resulted in an improved sensitivity of the specific antibody detection when used as solid‐phase antigen in ELISA. © 1997 European Peptide Society a

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199701)3:1<47::AID-PSC80>3.0.CO;2-V

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractThree peptides were isolated from bovine seminal plasma and purified to homogeneity. The amino acid sequences, as determined by FAB mass spectrometry, are the following:pGlu‐Ala‐ Glu‐Ser‐Asn‐OH,pGlu‐Ala‐Glu‐Ser(PO3H2‐Asn‐OH andpGlu‐Val‐Gly‐Glu‐Ser‐Glu‐Asn‐OH. These three peptides and some of their analogues were synthesized using liquid‐ and solid‐phase techniques. The pentapeptidepGlu‐Ala‐Glu‐Ser‐Asn‐OH showed a remarkable affinity for kinase NII and a strong inhibiting activity in DNA transcription. These findings support the hypothesis that phosphorylated acidic domains of nuclear non‐histone proteins could bind to DNA, thereby controlling transcription. © 1997

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199701)3:1<54::AID-PSC68>3.0.CO;2-9

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY

摘要:

AbstractLipid‐induced secondary structures and orientations of the two enantiomeric [Leu5]‐enkephalins,L‐Tyr‐Gly‐Gly‐L‐Phe‐L‐Leu, andD‐Tyr‐Gly‐Gly‐D‐Phe‐D‐Leu, on flat multi‐bilayers of 1‐palmitoyl‐2‐oleoyl‐sn‐ glycero‐3‐phosphocholine (POPC) were examined with polarized attenuated total reflection IR (IRATR) spectroscopy and molecular mechanics procedures. The membrane‐bound peptides showed identical IR spectra in the amide I and II band regions that indicated membrane‐induced secondary structures and specific orientations of the non‐zwitterionic molecules. A Lorentzian band shape analysis based on second derivatives of the original curves and the observed band polarizations suggested the presence of helical structures (βIII‐and α‐turns), oriented more or less perpendicular to the membrane surface. Other folded structures,e.g.βI‐ and γ turns, were not excluded. Molecular modelling of non‐zwitterionic [Leu5]‐enkephalin with two βIII‐turns or an α‐turn resulted in essentially four low‐energy conformers containing (i) two βIII‐turns, (ii) one α‐turn, (iii) a βIII‐turn fused to an α‐turn, and (iv) a βIII‐turn fused to a βI‐turn as in the crystallographic molecular conformation described by Aubryet al. [Biopolymers28, 27–40 (1989)]. Zwitterionic [Leu5]‐enkephalin with two βIII‐turns collapsed to a C13turn (a distorted α‐ turn) bridged by a γI‐turn (v). The alignment of the amide I oscillators within the helical structures, (i), (ii) and (iii), and the double‐bend structures, (iv) and (v), explained the observed amide I and II polarizations. Differences between these and other lipid‐induced [Leu5]‐enkephalin conformers reported in the literature may be caused by the lipid polymorphism of the model membranes used. Possible implications of the new conformers for the molecular mechanism of opioid receptor selection are

ISSN:1075-2617    

DOI:10.1002/(SICI)1099-1387(199701)3:1<65::AID-PSC90>3.0.CO;2-Q

出版商:John Wiley&Sons, Ltd.    

年代:1997

数据来源: WILEY