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At least 343 records · Page 19Linked to original sources
PubMed1996

Structure, localization and action of a novel inhibitory neuropeptide involved in the feeding of Lymnaea.

A neuropeptide that strongly inhibits the spontaneous contractions of the oesophagus in Lymnaea has been characterized as GAPRFVamide. Direct mass spectrometry of nervous tissues and immunocytochemical studies show that the peptide is synthesized by neurones in the buccal ganglia and transported to the oesophagus via the dorso-buccal nerve. In accordance with the function of the peptide, immunoreactive fibres are detected within the muscle layer of the oesophagus. Finally, mass spectrometry reveals the presence of a number of unidentified peptides in the nerves that innervate the oesophagus, which suggests that oesophageal activities may be modified by multiple peptides.

Animals↗
PubMed1994

Structure, localization, and action of buccalin B: a bioactive peptide from Aplysia.

The cholinergic motor neurons for the accessory radula closer (ARC) contain several neuropeptides that affect muscle contractions. In the present study, we have purified and sequenced a sixth ARC neuropeptide, using a combination of high pressure liquid chromatography and bioassays. This neuropeptide, Gly-Leu-Asp-Arg-Tyr-Gly-Phe-Val-Gly-Gly-Leu-amide, has been named buccalin B (BUCb) because it is significantly homologous to the previously characterized neuropeptide buccalin A. BUCb was found to be two-three times more potent than buccalin A in depressing motor neuron induced contractions.

Amino Acid Sequence↗
PubMed1995

Local structural difference between human and bovine band 3 in the anion transport inhibitor-binding region.

We have examined molecular properties of inhibitor-complexed human and bovine band 3, an anion transport protein of erythrocyte membrane, in order to demonstrate the structural characteristics of the inhibitor binding region. Band 3 modified with DIDS (4,4'-diisothiocyano-2,2'-stilbenedisulfonate), a potent anion transport inhibitor, generated a positive circular dichroic band at a wavelength of 345 nm, corresponding to a DIDS chromophore. The dichroic spectra of human band 3-DIDS complex and its bovine counterpart differed markedly in their ellipticity. Under the conditions that H2DIDS (the dihydro-derivative of DIDS) cross-linked two chymotryptic fragments of human band 3, the reagent failed to cross-link the equivalent bovine fragments. The inhibitory effect of PLP (pyridoxal 5'-phosphate), a substrate and affinity label, on phosphate influx into red blood cells was more pronounced for human band 3 than for bovine band 3. The residue Lys-562 of human band 3 was found to be modified with PLP, while the corresponding residue of bovine band 3 was devoid of reactivity with PLP.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2005

Importance of local structures of second and third repeat fragments of microtubule-binding domain for tau filament formation.

To investigate the importance of the seventh residue of the second and third repeat fragments (R2 and R3 peptides) of the microtubule-binding domain (MBD) for tau filamentous assembly, the residues Lys and Pro were substituted (R2-K7P and R3-P7K). The filament formations of the R2 and R3 peptides were almost lost due to their substitutions despite their overall conformational similarities. The NOE analyses showed the importance of the conformational flexibility for the R2 peptide and the coupled extended and helical conformations for the R3 peptide in their limited N-terminal regions around their seventh residues. The result shows that the filament formation of MBD is initiated from a short fragment region containing the minimal conformational or functional motif.

Amino Acid Sequence↗
PubMed2000

A solid-state NMR study of the phospholamban transmembrane domain: local structure and interactions with Ca(2+)-ATPase.

The structure and dynamics of a double (13)C-labelled 24-residue synthetic peptide ([(13)C(2)]CAPLB(29-52)), corresponding to the membrane-spanning sequence of phospholamban (PLB), were examined using (13)C cross-polarisation magic-angle spinning (CP-MAS) NMR spectroscopy. CP-MAS spectra of [(13)C(2)]CAPLB(29-52) reconstituted into unsaturated lipid membranes indicated that the peptide was mobile at temperatures down to -50 degrees C. The NMR spectra showed that peptide motion became constrained in the presence of the SERCA1 isoform of Ca(2+)-ATPase, and chemical cross-linking experiments indicated that [(13)C(2)]CAPLB(29-52) and Ca(2+)-ATPase came into close contact with one another. These results together suggested that the peptide and the 110-kDa calcium pump were interacting in the membrane. Rotational resonance CP-MAS (13)C-(13)C distance measurements on [(13)C(2)]CAPLB(29-52) reconstituted into lipid bilayers confirmed that the sequence spanning Phe-32 and Ala-36 was alpha-helical, and that this structure was not disrupted by interaction with Ca(2+)-ATPase. These results support the finding that the transmembrane domain of PLB is partially responsible for regulation of Ca(2+) transport through interactions with cardiac muscle Ca(2+)-ATPase in the lipid bilayer, and also demonstrate the feasibility of performing structural measurements on PLB peptides when bound to their physiological target.

Amino Acid Sequence↗
PubMed1977

Fine structural localization of glucose-6-phosphatase activity in the pancreatic islets of two amphibian species (Salamandra salamandra L. and Rana esculenta L.).

The ultrastructural distribution of glucose-6-phosphatase activity has been investigated in the salamander and frog pancreas. In the pancreas of salamander the enzyme was located in the A-cells, while in frog it occurred in all main types of islet cells B-, A-, and D-cells). As a rule, the reaction intensity was higher in the frog islet cells. No reaction was recorded in the exocrine pancreatic tissue of both species. The glucose-6-phosphatase activity was constantly detected in the lumen of rough endoplasmic reticulum and between the nuclear envelopes. Other enzyme localizations, observed especially in the A-cells of the salamander pancreas, were considered possible diffusion artifacts ro remnants of other phosphatase activity. The enzyme distribution in different types of islet cells, as well as its functional significance are discussed in relation to the findings of other authors.

Animals↗
PubMed1989

Fine structural localization of non-specific cholinesterase activity in rat tendon organs.

Electron microscopical localization of non-specific cholinesterase (nChE) activity was studied in tendon organs of the rat hindlimb muscles. The comparison between neurotendinous part (with high nChE activity) and purely collagenous compartment(s) (with very low nChE activity) demonstrated that Schwann cells are the fundamental source of this enzyme in rat tendon organs. Although particles of the nChE reaction product were also found in and around fibroblasts in both neurotendinous and purely collagenous compartments, their contribution to the overall nChE was not significant. nChE activity in rat tendon organs displayed heterogeneity along the Ib sensory axon; the highest activity was related to the Schwann cell investment of the unmyelinated part of Ib axon, lower activity to sensory terminals covered only by basement membrane and negligible activity to the myelinated part of sensory axons. Particles of the non-specific cholinesterase reaction product persisted in the basement membrane of Schwann cells 20 d after degeneration of Ib sensory axons and their terminals. The function of non-specific cholinesterase in sensory receptors is still not clear. It is suggested that this enzyme may be involved in the maintenance of the ionic milieu around sensory axon terminals during or after functional activity.

Animals↗
PubMed2002

Local structural changes caused by peptidyl-prolyl cis/trans isomerization in the native state of proteins.

Peptidyl-prolyl cis/trans isomerization, observed in the native state of an increasing number of proteins, is of considerable biological significance. The first evidence for an asymmetric transmission along the polypeptide chain of the structural effects of prolyl isomerization is now derived from the statistics of the C(alpha)/C(alpha)-atom distance distributions in the crystal structures of 848 non-homologous proteins. More detailed information on how isomerization affects segments adjacent to proline is obtained from crystal structures of proteins, that are more than 95% homologous, and that exhibit two different states of isomerization at a particular prolyl bond. The resulting 64 cases, which represent 3.8% of the database used, form pairs of coordinates which were analyzed for the existence of isomer-specific intramolecular nonbonded C(alpha)/C(alpha)-atom distances around the critical proline, and for the positional preferences for particular amino acids in the isomeric sequence segment. The probability that a native protein exhibits both prolyl isomers in the crystalline state increases in particular with a Pro at the third position N-terminal to the isomeric bond (-3 position), and with Ser, Gly and Asp at the position preceding the isomeric bond (-1 position). Structural alignment of matched pairs of isomeric proteins generates three classes with respect to position-specific distribution of C(alpha)-atom displacements around an isomeric proline imide bond. In the majority of cases the distribution of these intermolecular isomer-specific C(alpha)-atom distances shows a symmetric behavior for the N-terminal and C-terminal segment flanking the proline residue, and the magnitude did not exceed 1.3+/-0.6 A including the C(alpha) atoms in proximity to the prolyl bond. However, in the remaining 12 protein pairs the structural changes are unidirectional relative to the isomerizing bond whereby the magnitude of the isomer-specific effect exceeds 3.0+/-2.0 A even at positions remote to proline. Interestingly, the magnitude of the intramolecular isomer-specific C(alpha) atom displacements reveals a lever-arm amplification of the isomerization-mediated structural changes in a protein backbone. The observed backbone effects provide a structural basis for isomer-specific reactions of proline-containing polypeptides, and thus may play a role in biological recognition and regulation.

Crystallography, X-Ray↗
PubMed2001

The cloning, genomic structure, localization, and expression of human deoxyribonuclease IIbeta.

Acidic endonuclease activity is present in all cells in the body and much of this can be attributed to the previously cloned and ubiquitously expressed deoxyribonuclease II (DNase II). Database analysis revealed the existence of expressed sequence tags and genomic segments coding for a protein with considerable homology to DNase II. This report describes the cloning of this cDNA, which we term deoxyribonuclease IIbeta (DNase IIbeta) and comparison of its expression to that of the originally cloned DNase II (now termed DNase IIalpha). The cDNA encodes a 357 amino acid protein. This protein exhibits extensive homology to DNase IIalpha including an amino-terminal signal peptide and a conserved active site, and has many of the regions of identity that are conserved in homologs in other mammals as well as C. elegans and Drosophila. The gene encoding DNase IIbeta has identical splice sites to DNase IIalpha. Human DNase IIbeta is highly expressed in the salivary gland, and at low levels in trachea, lung, prostate, lymph node, and testis, whereas DNase IIalpha is ubiquitously expressed in all tissues. The expression pattern of human DNase IIbeta suggests that it may function primarily as a secreted enzyme. Human saliva was found to contain DNase IIalpha, but after immunodepletion, considerable acid-active endonuclease remained which we presume is DNase IIbeta. We have localized the gene for human DNase IIbeta to chromosome 1p22.3 adjacent (and in opposing orientation) to the human uricase pseudogene. Interestingly, murine DNase IIbeta is highly expressed in the liver. Uricase is also highly expressed in mouse but not human liver and this may explain the difference in expression patterns between human and mouse DNase IIbeta.

Amino Acid Sequence↗
PubMed1997

23Na chemical shifts and local structure in crystalline, glassy, and molten sodium borates and germanates.

A simple correlation between average Na-O bond length and 23Na isotropic chemical shift in crystalline germanates and borates has been established, similar to existing correlations for sodium in silicates and carbonates. This empirical trend is discussed in terms of a decreasing paramagnetic contribution to the chemical shift with increasing average bond length. The correlation is then applied to data for sodium borate and germanate glasses and melts from room temperature to 1200 degrees C, where both structural and compositional effects on the chemical shift are apparent.

Borates↗
PubMed1994

Extensively methylated myosin subfragment-1: examination of local structure, interactions with nucleotides and actin, and ligand-induced conformational changes.

The atomic structure of myosin subfragment-1 (S1) has been recently solved for crystals of extensively methylated S1 [Rayment et al. (1993) Science 261, 50-58]. In this study, the effect of such a modification on S1 structure and function was examined. According to the far- and near-ultraviolet CD spectra, the methylation does not affect the secondary structure of S1 but causes limited changes in its tertiary structure. The methylation significantly decreases the affinity of S1 for actin in rigor and, to a lesser degree, that of S1 to actin in the presence of MgATP gamma S. This modification, like the trinitrophenylation of Lys-83, accelerates the dissociation of a nucleotide trapped on S1 either by phosphate analogs or by cross-linking of the SH1 and SH2 thiols. Methylation strongly impairs the coupling between the actin- and nucleotide-binding sites as revealed by the reduced effect of actin on the release of epsilon ADP from the active site. It also causes a complete loss of in vitro motility of actin filaments over methylated HMM. In addition to this, methylation also impairs the communication between other sites on S1 including that between the nucleotide-binding site and SH1, and the actin-binding site and the 27/50 kDa junction and a site at 74 kDa from the N-terminus of S1. These changes are revealed in SH1 modification, thermolysin digestion, and vanadate-dependent photocleavage experiments, respectively. The increased rate of thermal denaturation of S1 and the loss of S1 protection by ADP and actin from this process also indicate flawed communications in methylated S1. It is concluded that these relatively mild but numerous and important changes impair the function of methylated S1.

Actins↗