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1.
Three myotropic peptides belonging to the Arg-amide insect tachykinin family were isolated from whole-body extracts of the mosquito, Culex salinarius. The peptides, APSGFMGMR-NH2, APYGFTGMR-NH2 and APSGFFGMR-NH2 (designated culetachykinin I, II, and III) were isolated and purified on the basis of their ability to stimulate muscle contractions of isolated Leucophaea maderae hindgut. Biologically inactive methionine sulfoxides of two of the three peptides were isolated using an ELISA system based upon antiserum raised against APYGFTGMR-NH2 and identified with mass spectrometry. Immunocytochemistry localized these peptides in cells in the brain, antennae, subesophageal, thoracic and abdominal ganglion, proventriculus and midgut. Nerve tracts containing these peptides were found in the median nerve of the brain, central body, nervi corpus cardiaci, cervical nerve, antennal lobe and on the surface of the midgut.  相似文献   

2.
Summary Extracts of corpora cardiaca from two members of the family Tenebrionidae,Zophobas rugipes andTenebrio molitor, from one member of the Chrysomelidae,Leptinotarsa decemlineata, and from three members of the Scarabaeidae,Pachnoda marginata, P. sinuata andMelolontha hippocastani, were assayed for adipokinetic and hypertrehalosaemic activity in acceptor locusts (Locusta migratoria) and cockroaches (Periplaneta americana), respectively. All corpus cardiacum material tested, except that from the cockchafer,M. hippocastani, gave positive bioassay results. Biological activities of corpus cardiacum extracts from all species investigated can be resolved on reversed-phase high performance liquid chromatography (RP-HPLC). Gland extracts from the two tenebrionid species each show a single peak of biological activity associated with a single peak of UV absorbance having an identical retention time in both species. The two biologically active fractions from the corpora cardiaca of the potato beetle,L. decemlineata, coelute with exogenous (synthetic) hypertrehalosaemic hormones I and II of the American cockroach. The two species of the genusPachnoda contain two active compounds in their glands; compound I of each species is more abundant and elutes just ahead of the (synthetic) hypertrehalosaemic hormone of the cockroachBlaberus discoidalis. The gland material ofM. hippocastani exhibits and absorbance peak with the same retention time as the major peak from thePachnoda-species; however, this peak material does not elicit biological activity in the assays used here. After fractionation by RP-HPLC the main biologically active compounds were subjected to amino acid analyses. All factors are peptidic and contain 8 amino acid residues. The peptides from the tenebrionid species have the amino acid residues Asx(2), Glx(1), Ser(1), Pro(1), Leu(1), Phe(1) and Trp(i), whereas the main peptide from corpora cardiaca ofP. marginata contains the residues Asx(2), Glx(1), Ser(1), Pro(1), Tyr(1), Leu(1) and Trp(1). Amino acid composition analyses of the two active fractions fromL. decemlineata reveal the residues Asx(2), Glx(1), Ser(1), Pro(1), Val(1), Phe(1) and Trp(1) for compound I and Asx(1), Glx(1), Thr(2), Pro(1), Leu(1), Phe(1) and Trp(1) for compound II.  相似文献   

3.
The distribution of neurones immunoreactive to antisera raised against the undecapeptide C-terminal fragment of drosulfakinin II (DrmSKII), Asp-Gln-Phe-Asp-Asp-Tyr(SO3H)-Gly-His-Met-Arg-Phe-NH2, has been studied in the blowfly Calliphora vomitoria. Antisera were preabsorbed with combinations of the parent antigen, the tetrapeptide Phe-Met-Arg-Phe-NH2 and cholecystokinin, the vertebrate sulfated octapeptide (CCK-8), Asp-Tyr(SO3H)-Met-Gly-Trp-Met-Asp-Phe-NH2, in order to ensure specificity for the sulfakinin peptides of C. vomitoria (the nonapeptide callisulfakinin I is identical to drosulfakinin I and callisulfakinin II differs from DrmSK II only by the presence of -Glu3-Glu4- in place of -Asp3-Asp4-). Only four pairs of sulfakinin-immunoreactive neurones have been visualised in the entire nervous system. These occur in the brain: two pairs of cells situated medially in the caudo-dorsal region close to the roots of the ocellar nerve and two other pairs at the same level but positioned more laterally. Despite the small number of sulfakinin-immunoreactive cells, there are extensive projections to many areas of neuropile in the brain and the thoracic ganglion. The pathway of the medial sulfakinin cells extends into each of the three thoracic ganglia and a metameric arrangement of sulfakinin neuronal projections is also seen in the abdominal ganglia. Neither the dorsal neural sheath of the thoracic ganglion, nor the abdominal nerves contain sulfakinin-immunoreactive material. These observations suggest that the sulfakinins of the blowfly function as neurotransmitters or neuromodulators. They do not appear to have a direct role in gut physiology, as has been shown by in vitro bioassays for the sulfakinins of orthopterans and blattodeans. In addition to the neurones that display specific sulfakinin immunoreactivity, other cells within the brain and thoracic ganglion are immunoreactive to cholecystokinin/gastrin antisera. There are, therefore, at least two types of dipteran neuropeptides with amino acid sequences that are similar to the vertebrate molecules cholecystokinin and gastrin.  相似文献   

4.
ABSTRACT

γ-glutamyl peptides have been suggested to impart kokumi properties to foods by activating human calcium-sensing receptor (hCaSR). In this study, the relationship between γ-glutamyl peptide structure and hCaSR activity was systematically analyzed using γ-[Glu](n=0-4)-α-[Glu](n=0-3)-Tyr. Our results suggest that N-terminal [Glu]3 moiety is very important for hCaSR activities of γ-glutamyl peptides.  相似文献   

5.
An α-amylase from Aspergillus oryzae, Taka-amylase A (TAA), was cleaved into peptide fragments by an acid protease. Inactivation of TAA was greatly retarded by the addition of α-cyclodextrin or Ca2+. TAA peptide fragments were separated into two groups having no and high affinity to the substrate, soluble starch. This separation was done by the forced affinity chromatography method by a column of epichlorohydrin cross-linked soluble starch gel. Three peptides were isolated from the high-affinity fragments, purified by the ODS-120T column, and their amino acids were sequenced. Peptides I, II, and III originated from α2-helix, α3-helix, and β2-sheet, respectively, and all of these were located in the (β/α)8 barrel of the main domain of TAA molecule. A stereo graphic view showed that Peptides I–III were at the cleft near the catalytic site. Occurrence of a Trp residue in all three peptides strongly suggested that Trp was very important in the binding of TAA to the substrate, soluble starch.  相似文献   

6.
Two aldehydic C20-gibberellins, L-2 and L-4, were isolated from the immature fruits of yellow lupine (Lupinus luteus L.). L-2 was shown to have the structure II and named gibberellin A23. L-4 was identified as gibberellin A19(VI). Two new C20-gibberellins, tentatively called 3,13-dihydroxy GA15(IV) and 13-hydroxy GA15(VIII), were derived from gibberellins, A23 and A19, respectively. The biological activities of four 3,13-dihydroxy C20-gibberellins-GA18(I), GA23(II), GA28(III) and 3,13-dihydroxy GA15(IV), which were isolated from the fruits except for 3,13-dihydroxy GA15—were compared in six gibberellin bioassays.  相似文献   

7.
Protein folding problem remains a formidable challenge as main chain, side chain and solvent interactions remain entangled and have been difficult to resolve. Alanine‐based short peptides are promising models to dissect protein folding initiation and propagation structurally as well as energetically. The effect of N‐terminal diproline and charged side chains is assessed on the stabilization of helical conformation in alanine‐based short peptides using circular dichroism (CD) with water and methanol as solvent. A1 (Ac–Pro–Pro–Ala–Lys–Ala–Lys–Ala–Lys–Ala–NH2) is designed to assess the effect of N‐terminal homochiral diproline and lysine side chains to induce helical conformation. A2 (Ac–Pro–Pro–Glu–Glu–Ala–Ala–Lys–Lys–Ala–NH2) and A3 (Ac–d Pro–Pro–Glu–Glu–Ala–Ala–Lys–Lys–Ala–NH2) with N‐terminal homochiral and heterochiral diproline, respectively, are designed to assess the effect of Glu...Lys (i , i  + 4) salt bridge interactions on the stabilization of helical conformation. The CD spectra of A1 , A2 and A3 in water manifest different amplitudes of the observed polyproline II (PPII) signals, which indicate different conformational distributions of the polypeptide structure. The strong effect of solvent substitution from water to methanol is observed for the peptides, and CD spectra in methanol evidence A2 and A3 as helical folds. Temperature‐dependent CD spectra of A1 and A2 in water depict an isodichroic point reflecting coexistence of two conformations, PPII and β‐strand conformation, which is consistent with the previous studies. The results illuminate the effect of N‐terminal diproline and charged side chains in dictating the preferences for extended‐β, semi‐extended PPII and helical conformation in alanine‐based short peptides. The results of the present study will enhance our understanding on stabilization of helical conformation in short peptides and hence aid in the design of novel peptides with helical structures. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.  相似文献   

8.
The dehydro-residue containing peptides N-Ac-dehydro-Phe-L -Leu-OCH3 ( I ) and N-Ac-dehydro-Phe-NorVal-OCH3 ( II ) were synthesized by the usual workup procedures. The peptides crystallize from their solutions in methanol in space group P65: ( I ) a = b = 12.528(2) Å, c = 21.653(5) Å; ( II ) a = b = 12.532(2) Å, c = 21.695(4) Å. The structures were determined by direct methods. Both peptides adopt similar conformations with ?,ψ of dehydro-Phe as follows: ( I ) ?57.0(5)° and ?37.0(5)°; ( II ) ?56.0(5),° and ?37.5(5)°. The observed data on dehydro-Phe when placed at the (i + 1) position show that the ?,ψ values of dehydro-Phe are either ?60°, 140° or ?60°, ?30°. The conformation of ?60°, 140° can be accommodated only with a flexible residue at the (i + 2) position while the ?,ψ values of ?60°, ?30° are obtained with a bulky residue at the (i + 2) position as in the present structures. The molecules are packed in a helical way along the c axis. These are held by two strong intermolecular hydrogen bonds involving both NH as donors and acetyl group and dehydro-Phe oxygen atoms as acceptors. © 1994 John Wiley & Sons, Inc.  相似文献   

9.
C M Deber  P D Adawadkar 《Biopolymers》1979,18(10):2375-2396
We have synthesized and characterized a series of cation-binding cyclic octapeptides which may function as potential ionophoric substances. The materials contain varying degrees of hydrophobic character, which was controlled systematically through the incorporation of N-alkylglycine residues where N-alkyl = methyl, n-hexyl, cyclohexyl, or n-decyl. The peptides reported include cyclo(Phe-Sar-Gly-Sar)2, cyclo(Glu(OBzl)-Sar-Gly-Sar-Glu(OBzl)-Sar-Gly-(N-decyl)Gly), cyclo(Glu(OBzl)-Sar-Gly-(N-decyl)Gly)2, cyclo(Glu(OBzl)-Sar-Gly-(N-hexyl)Gly)2, cyclo(Glu(OBzl)-Sar-Gly-(N-cyclohexyl)Gly)2, and the corresponding free diacid forms of the Glu-containing compounds. Using 13C- and 1H-nmr spectra, we demonstrated that the mixture of cis/trans peptide bond-isomer conformers, characteristic of the free-peptide benzyl esters in solution, was converted to unique C2-symmetric, presumably all-trans conformers on complexation with calcium ions. Cation-transport experiments, using the thick-liquid model of transport in a Pressman cell, established that these compounds transport a variety of cations and that one peptide examined in detail, cyclo(Glu(OBzl)-Sar-Gly-(N-decyl)Gly)2 (selectivity Ca2+ > Na+ > K+ > Mn2+ > Cu2+ > Mg2+ > Co2+ > Zn2+), transports calcium about an order of magnitude more efficiently than magnesium.  相似文献   

10.
Following the rapid uplift of the Qinghai-Tibetan Plateau, the reorganization of the major river drainages in southwest China was primarily caused by river capture events. However, the impact of these past changes in drainage patterns on the current distribution and genetic structure of the endemic flora of this region remains largely unknown. Here we report a survey of amplified fragment length polymorphism (AFLP) in Terminalia franchetii, an endemic shrub or small tree of the deep and dry-hot river valleys of this region. We surveyed AFLP variation within and among 21 populations (251 individuals) of T. franchetii, distributed disjunctively between northern and southern drainage systems. Using STRUCTURE, principal coordinates analysis, and genetic distance methods, we identified two main population genetic groups (I and II) and four subgroups within the species, as follows: (I) the Upper Jinshajiang Valley (subgroup I(north)) and the Honghe drainage area (subgroup I(south)); (II) the Middle and Lower Jinshajiang and Yalongjiang Valleys (subgroup II(north)) and the Nanpanjiang drainage area (subgroup II(south)). Genetic diversity was lower in group I than in group II. According to the genetic diversity and genetic structure results, we suggest that the modern disjunctive distribution and associated patterns of genetic structure of T. franchetii result from vicariance caused by several historical drainage capture events, involving the separation of the Upper Jinshajiang, Yalongjiang and Daduhe from the Honghe or Nanpanjiang in southwest China.  相似文献   

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