scholarly journals Properties of potato lectin and the nature of its glycoprotein linkages

1978 ◽  
Vol 171 (3) ◽  
pp. 665-674 ◽  
Author(s):  
Anthony K. Allen ◽  
Nila N. Desai ◽  
Albert Neuberger ◽  
J. Michael Creeth
Keyword(s):  
Polypeptide Chain ◽  
Ph Value ◽  
High Viscosity ◽  
Inhibitory Effect ◽  
Natural Occurrence ◽  
Amino Acid Residues ◽  
Plant Glycoproteins ◽  
Coffee Beans ◽  
Hydroxy Groups ◽  
Potato Lectin

1. Potato lectin is a glycoprotein that contains about 47% (by weight) l-arabinose, 3% d-galactose and 11% hydroxyproline. It has a monomeric molecular weight of about 50000 and probably exists as a monomer–dimer system in aqueous solution, with the monomer predominating. It has a very high viscosity, which would indicate either that the molecule is very expanded or that it is an elongated ellipsoid. 2. After prolonged proteolytic digestion of a reduced and carboxymethylated derivative of the lectin, a glycopeptide was isolated (of mol.wt. 32000–34000) that included all the carbohydrate and hydroxyproline of the original glycoprotein but less than 30% of the total original amino acid residues. 3. The arabinose of the glycoprotein is present exclusively as the β-arabinofuranoside and this includes those residues that are directly linked to the hydroxyproline residues of the polypeptide chain. All the arabinose of the glycoprotein is linked to the polypeptide chain through the hydroxyproline residues; the ratio of arabinose to hydroxyproline is 3.4:1. Although α-arabinofuranosides are known to be present in arabinans and arabinogalactans, the natural occurrence of β-arabinofuranosides has not previously been reported. 4. Nine or ten serine residues of the polypeptide chain are substituted with single α-galactopyranoside residues that can be removed by the action of α-galactosidase from coffee beans but not by a β-galactosidase. This is the first report of an α-galactoside linkage to serine. The effect of α-galactosidase is much greater on a glycopeptide from which the arabinose has been already removed, which indicates a steric hindrance of the galactosidase action by adjacent chains of arabinosides. 5. In 0.5m-NaOH (pH13.7), galactose residues were removed from the serine residues of the glycopeptide by a process of β-elimination. This reaction took place very slowly in the intact glycopeptide but much more rapidly when the arabinofuranoside residues had been removed. This inhibitory effect of the arabinofuranoside residues on the β-elimination reaction is likely to be due to a negative charge on the hydroxy groups of the adjacent arabinofuranoside residues, which would be ionized at this high pH value. 6. It is suggested that potato lectin may be representative of a class of soluble plant glycoproteins that would include precursors of the cell-wall glycoprotein extensin. If this is the case, extensin should also contain β-l-arabinofuranosides linked to hydroxyproline and α-d-galactopyranosides linked to serine residues of the polypeptide chain.

Effect of human galanin on the response of circulating catecholamines to hypoglycemia in man

1995 ◽  
Vol 133 (6) ◽  
pp. 723-728 ◽  
Author(s):  
Ettore C degli Uberti ◽  
Maria R Ambrosio ◽  
Marta Bondanelli ◽  
Giorgio Transforini ◽  
Alberto Valentini ◽  
...  
Keyword(s):  
Heart Rate ◽  
Healthy Subjects ◽  
Sympathetic Nerve Activity ◽  
Heart Rate Response ◽  
Statistical Significance ◽  
Inhibitory Effect ◽  
Amino Acid Residues ◽  
Nerve Activity ◽  
Receptor Stimulation

degli Uberti EC, Ambrosio MR, Bondanelli M, Trasforini G, Valentini A, Rossi R, Margutti A, Campo M. Effect of human galanin on the response of circulating catecholamines to hypoglycemia in man. Eur J Endocrinol 1995;133:723–8. ISSN 0804–4643 Human galanin (hGAL) is a neuropeptide with 30 amino acid residues that has been found in the peripheral and central nervous system, where it often co-exists with catecholamines. In order to clarify the possible role of hGAL in the regulation of sympathoadrenomedullary function, the effect of a 60 min infusion of hGAL (80 pmol·kg−1 · min−1) on plasma epinephrine and norepinephrine responses to insulin-induced hypoglycemia in nine healthy subjects was investigated. Human GAL administration significantly reduced both the release of basal norepinephrine and the response to insulin-induced hypoglycemia, whereas it attenuated the epinephrine response by 26%, with the hGAL-induced decrease in epinephrine release failing to achieve statistical significance. Human GAL significantly increased the heart rate in resting conditions and clearly exaggerated the heart rate response to insulin-induced hypoglycemia, whereas it had no effect on the blood pressure. We conclude that GAL receptor stimulation exerts an inhibitory effect on basal and insulin-induced hypoglycemia-stimulated release of norepinephrine. These findings provide further evidence that GAL may modulate sympathetic nerve activity in man but that it does not play an important role in the regulation of adrenal medullary function. Ettore C degli Uberti, Chair of Endocrinology, University of Ferrara, Via Savonarola 9, I-44100 Ferrara, Italy

Amino acid sequence of cyanogen bromide fragment CB5 of human hemopexin

1989 ◽  
Vol 54 (3) ◽  
pp. 803-810 ◽  
Author(s):  
Ivan Kluh ◽  
Ladislav Morávek ◽  
Manfred Pavlík
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Acid Hydrolysis ◽  
Cyanogen Bromide ◽  
Polypeptide Chain ◽  
Amino Acid Residues ◽  
Mild Acid Hydrolysis ◽  
Methionine Residue ◽  
Cyanogen Bromide Fragment ◽  
Mild Acid

Cyanogen bromide fragment CB5 represents the region of the polypeptide chain of hemopexin between the fourth and fifth methionine residue (residues 232-352). It contains 120 amino acid residues in the following sequence: Arg-Cys-Ser-Pro-His-Leu-Val-Leu-Ser-Ala-Leu-Thr-Ser-Asp-Asn-His-Gly-Ala-Thr-Tyr-Ala-Phe-Ser-Gly-Thr-His-Tyr-Trp-Arg-Leu-Asp-Thr-Ser-Arg-Asp-Gly-Trp-His-Ser-Trp-Pro-Ile-Ala-His-Gln-Trp-Pro-Gln-Gly-Pro-Ser-Ala-Val-Asp-Ala-Ala-Phe-Ser-Trp-Glu-Glu-Lys-Leu-Tyr-Leu-Val-Gln-Gly-Thr-Gln-Val-Tyr-Val-Phe-Leu-Thr-Lys-Gly-Gly-Tyr-Thr-Leu-Val-Ser-Gly-Tyr-Pro-Lys-Arg-Leu-Glu-Lys-Glu-Val-Gly-Thr-Pro-His-Gly-Ile-Ile-Leu-Asp-Ser-Val-Asp-Ala-Ala-Phe-Ile-Cys-Pro-Gly-Ser-Ser-Arg-Leu-His-Ile-Met. The sequence was derived from the data on peptides prepared by cleavage of fragment CB5 by mild acid hydrolysis, by trypsin and chymotrypsin.

Molecular Mechanisms of the Inhibitory Effects of Bupivacaine, Levobupivacaine, and Ropivacaine on Sarcolemmal Adenosine Triphosphate–sensitive Potassium Channels in the Cardiovascular System

2004 ◽  
Vol 101 (2) ◽  
pp. 390-398 ◽  
Author(s):  
Takashi Kawano ◽  
Shuzo Oshita ◽  
Akira Takahashi ◽  
Yasuo Tsutsumi ◽  
Yoshinobu Tomiyama ◽  
...  
Keyword(s):  
Cardiovascular System ◽  
Adenosine Triphosphate ◽  
Local Anesthetics ◽  
Molecular Mechanisms ◽  
Transmembrane Domain ◽  
Katp Channels ◽  
Inhibitory Effect ◽  
Amino Acid Residues ◽  
Sulfonylurea Receptor ◽  
Inhibitory Effects

Background Sarcolemmal adenosine triphosphate-sensitive potassium (KATP) channels in the cardiovascular system may be involved in bupivacaine-induced cardiovascular toxicity. The authors investigated the effects of local anesthetics on the activity of reconstituted KATP channels encoded by inwardly rectifying potassium channel (Kir6.0) and sulfonylurea receptor (SUR) subunits. Methods The authors used an inside-out patch clamp configuration to investigate the effects of bupivacaine, levobupivacaine, and ropivacaine on the activity of reconstituted KATP channels expressed in COS-7 cells and containing wild-type, mutant, or chimeric SURs. Results Bupivacaine inhibited the activities of cardiac KATP channels (IC50 = 52 microm) stereoselectively (levobupivacaine, IC50 = 168 microm; ropivacaine, IC50 = 249 microm). Local anesthetics also inhibited the activities of channels formed by the truncated isoform of Kir6.2 (Kir6.2 delta C36) stereoselectively. Mutations in the cytosolic end of the second transmembrane domain of Kir6.2 markedly decreased both the local anesthetics' affinity and stereoselectivity. The local anesthetics blocked cardiac KATP channels with approximately eightfold higher potency than vascular KATP channels; the potency depended on the SUR subtype. The 42 amino acid residues at the C-terminal tail of SUR2A, but not SUR1 or SUR2B, enhanced the inhibitory effect of bupivacaine on the Kir6.0 subunit. Conclusions Inhibitory effects of local anesthetics on KATP channels in the cardiovascular system are (1) stereoselective: bupivacaine was more potent than levobupivacaine and ropivacaine; and (2) tissue specific: local anesthetics blocked cardiac KATP channels more potently than vascular KATP channels, via the intracellular pore mouth of the Kir6.0 subunit and the 42 amino acids at the C-terminal tail of the SUR2A subunit, respectively.

scholarly journals Evaluation of Enzyme Inhibitory Activity of Flavonoids by Polydopamine-Modified Hollow Fiber-Immobilized Xanthine Oxidase

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3931
Author(s):  
Cong-Peng Zhao ◽  
Guo-Ying Chen ◽  
Yuan Wang ◽  
Hua Chen ◽  
Jia-Wen Yu ◽  
...  
Keyword(s):  
Xanthine Oxidase ◽  
Hollow Fiber ◽  
Inhibitory Activity ◽  
Ph Value ◽  
Enzymatic Reaction ◽  
Amino Acid Residues ◽  
Reaction Conditions ◽  
Docking Analysis ◽  
Dopamine Concentration ◽  
Immobilization Time

In this study, a polydopamine (PDA)-modified hollow fiber-immobilized xanthine oxidase (XOD) was prepared for screening potential XOD inhibitors from flavonoids. Several parameters for the preparation of PDA-modified hollow fiber-immobilized XOD, including the dopamine concentration, modification time, XOD concentration and immobilization time, were optimized. The results show that the optimal conditions for immobilized XOD activity were a dopamine concentration of 2.0 mg/mL in 10.0 mM Tris-HCl buffer (pH 8.5), a modification time of 3.0 h, an XOD concentration of 1000 μg/mL in 10.0 mM phosphate buffer (pH 7.5) and an immobilization time of 3.0 h. Subsequently, the enzymatic reaction conditions such as the pH value and temperature were investigated, and the enzyme kinetics and inhibition parameters were determined. The results indicate that the optimal pH value (7.5) and temperature (37 °C) of the PDA-modified hollow fiber-immobilized XOD were consistent with the free enzyme. Moreover, the PDA-modified hollow fiber-immobilized XOD could still maintain above 50% of its initial immobilized enzyme activity after seven consecutive cycles. The Michaelis–Menten constant (Km) and the half-maximal inhibitory concentration (IC50) of allopurinol on the immobilized XOD were determined as 0.25 mM and 23.2 μM, respectively. Furthermore, the PDA-modified hollow fiber-immobilized XOD was successfully applied to evaluate the inhibitory activity of eight flavonoids. Quercetin, apigenin, puerarin and epigallocatechin showed a good inhibition effect, and their percentages of inhibition were (79.86 ± 3.50)%, (80.98 ± 0.64)%, (61.15 ± 6.26)% and (54.92 ± 0.41)%, respectively. Finally, molecular docking analysis further verified that these four active compounds could bind to the amino acid residues in the XOD active site. In summary, the PDA-modified hollow fiber-immobilized XOD is an efficient method for the primary screening of XOD inhibitors from natural products.

scholarly journals Bile-pigment formation from different leghaemoglobins. Methine-bridge specificity of coupled oxidation

1978 ◽  
Vol 176 (2) ◽  
pp. 359-364 ◽  
Author(s):  
Päivi Lehtovaara ◽  
Ulla Perttilä
Keyword(s):  
Amino Acid ◽  
Polypeptide Chain ◽  
Broad Bean ◽  
Amino Acid Sequences ◽  
Second Step ◽  
Bile Pigment ◽  
Site Specificity ◽  
Amino Acid Residues ◽  
Reaction Step ◽  
Pigment Formation

The coupled oxidation of leghaemoglobins with O2 and ascorbate yielded oxyleghaemoglobin in the first reaction step, and the second step was the degradation of haem characterized by an A675 increase. Leghaemoglobins were degraded to biliverdin isomers specifically, depending on the structure of the protein. The main leghaemoglobin components of Glycine (soya bean) and Phaseolus (kidney bean) were degraded to biliverdin mixtures containing about 50% of the β-form, about 30% of the α-form and about 20% of the δ-isomer, whereas the leghaemoglobin I components of Vicia (broad bean) and Pisum (pea) were degraded almost exclusively to the β-isomer, with traces of the α-isomer. The amino acid sequences of Glycine and Phaseolus leghaemoglobins resemble each other, as do those of Vicia and Pisum. The site specificity of bile-pigment formation from leghaemoglobins can be tentatively explained by specific differences in the amino acid sequences at those regions of the polypeptide chain that are in the vicinity of the appropriate methine bridges. The ligand-binding site in different leghaemoglobins may be outlined on the basis of the present results, supposing that the haem is degraded when a reduction product of haem-bound O2 reacts with a methine bridge of the haem, and that the bridge specificity is regulated by hindering amino acid residues that determine the location of the bound O2. The residue phenylalanine-CD1 appears to be further away from the haem plane or in a markedly more flexible position in leghaemoglobins than in mammalian globins. The haem-bound oxygen atom B, in Fe–O(A)–O(B), seems to be free to rotate in all directions except that of the γ-bridge in Glycine and Phaseolus leghaemoglobins, but its position in Vicia and Pisum leghaemoglobin I might be restricted to the direction of the β-methine bridge.

The effect of plant metabolites on coronaviruses: A comprehensive review focusing on their IC50 values and molecular docking scores

2021 ◽  
Vol 21 ◽  
Author(s):  
Parastou Farshi ◽  
Eda Ceren Kaya ◽  
Fataneh Hashempour-Baltork ◽  
Kianoush Khosravi-Darani
Keyword(s):  
Molecular Docking ◽  
Inhibitory Effect ◽  
Organosulfur Compounds ◽  
Amino Acid Residues ◽  
Plant Metabolites ◽  
Primary Metabolites ◽  
Secondary Plant Metabolites ◽  
Protein Receptors ◽  
Ic50 Values ◽  
Natural Drugs

: Coronaviruses have caused worldwide outbreaks in different periods. SARS (severe acute respiratory syndrome), was the first emerged virus from this family, followed by MERS (Middle East respiratory syndrome) and SARS-CoV-2 (2019-nCoV or COVID 19), which is newly emerged. Many studies have been conducted on the application of chemical and natural drugs for treating these coronaviruses and they are mostly focused on inhibiting the proteases of viruses or blocking their protein receptors through binding to amino acid residues. Among many substances which are introduced to have an inhibitory effect against coronaviruses through the mentioned pathways, natural components are of specific interest. Secondary and primary metabolites from plants, are considered as potential drugs to have an inhibitory effect on coronaviruses. IC50 value (the concentration in which there is 50% loss in enzyme activity), molecular docking score and binding energy are parameters to understand the ability of metabolites to inhibit the specific virus. In this study we did a review of 154 papers on the effect of plant metabolites on different coronaviruses and data of their IC50 values, molecular docking scores and inhibition percentages are collected in tables. Secondary plant metabolites such as polyphenol, alkaloids, terpenoids, organosulfur compounds, saponins and saikosaponins, lectins, essential oil, and nicotianamine, and primary metabolites such as vitamins are included in this study.

Model of a folded polypeptide chain

1950 ◽  
Vol 137 (886) ◽  
pp. 79-79
Keyword(s):  
Amino Acid ◽  
Polypeptide Chain ◽  
Molecular Model ◽  
Polymer Chains ◽  
Side Chains ◽  
Amino Acid Residues ◽  
Infra Red ◽  
New Type ◽  
Folded Proteins ◽  
Red Radiation

The models on view in the ante-room show a way of folding a polypeptide chain which is consistent with some observations we have recently made with polarized infra-red radiation (Ambrose & Hanby 1949; Ambrose, Elliott & Temple 1949). The α -folded proteins, keratin, myosin and tropomyosin, have been found when oriented to show greater absorption of the N-H frequency when the electric vector of the absorbed radiation is in the direction of the fibre axis, hence the N-H bond must be preferentially oriented in this direction. A study of models has suggested that the only likely folding of the polypeptide chain consistent with this fact involves a seven-membered ring containing two amino-acid residues; the ring is completed by hydrogen bonds: A new type of atomic model which has been developed in our laboratories has been used. The scale is 0·8 in. to the Angstrom unit. The valency links, while allowing free rotation about single co-valent bonds, also allow some distortion of the bond angles when strains occur but are strong enough to allow long polymer chains to be built. The molecular model exhibited shows twenty-four amino-acid residues, with side chains on one side of the back-bone, representative of those occurring in myosin; the side chains on the other side have been removed for clearness and their positions indicated by single carbon atoms.

scholarly journals Characterization of COMMD protein–protein interactions in NF-κB signalling

2006 ◽  
Vol 398 (1) ◽  
pp. 63-71 ◽  
Author(s):  
Prim de Bie ◽  
Bart van de Sluis ◽  
Ezra Burstein ◽  
Karen J. Duran ◽  
Ruud Berger ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Copper Metabolism ◽  
Nuclear Factor Κb ◽  
Inhibitory Effect ◽  
Protein Family ◽  
Amino Acid Residues ◽  
Protein Protein Interactions ◽  
Necrosis Factor

COMMD [copper metabolism gene MURR1 (mouse U2af1-rs1 region 1) domain] proteins constitute a recently identified family of NF-κB (nuclear factor κB)-inhibiting proteins, characterized by the presence of the COMM domain. In the present paper, we report detailed investigation of the role of this protein family, and specifically the role of the COMM domain, in NF-κB signalling through characterization of protein–protein interactions involving COMMD proteins. The small ubiquitously expressed COMMD6 consists primarily of the COMM domain. Therefore COMMD1 and COMMD6 were analysed further as prototype members of the COMMD protein family. Using specific antisera, interaction between endogenous COMMD1 and COMMD6 is described. This interaction was verified by independent techniques, appeared to be direct and could be detected throughout the whole cell, including the nucleus. Both proteins inhibit TNF (tumour necrosis factor)-induced NF-κB activation in a non-synergistic manner. Mutation of the amino acid residues Trp24 and Pro41 in the COMM domain of COMMD6 completely abolished the inhibitory effect of COMMD6 on TNF-induced NF-κB activation, but this was not accompanied by loss of interaction with COMMD1, COMMD6 or the NF-κB subunit RelA. In contrast with COMMD1, COMMD6 does not bind to IκBα (inhibitory κBα), indicating that both proteins inhibit NF-κB in an overlapping, but not completely similar, manner. Taken together, these data support the significance of COMMD protein–protein interactions and provide new mechanistic insight into the function of this protein family in NF-κB signalling.

scholarly journals Anti-M monoclonal antibodies cross-reacting with variant Mg antigen: an example of modulation of antigenic properties of peptide by its glycosylation

Blood ◽  
1994 ◽  
Vol 84 (7) ◽  
pp. 2340-2345 ◽  
Author(s):  
E Jaskiewicz ◽  
M Czerwinski ◽  
D Syper ◽  
E Lisowska
Keyword(s):  
Monoclonal Antibodies ◽  
Amino Acid ◽  
Blood Group ◽  
Polypeptide Chain ◽  
Protein Glycosylation ◽  
Glycophorin A ◽  
Amino Acid Residues ◽  
Terminal Portion ◽  
Peptide Analogs ◽  
Antigenic Properties

Abstract Some monoclonal antibodies (MoAbs) directed against blood group M- related epitope of glycophorin A (GPA) were found to agglutinate rare variant erythrocytes carrying GPA of Mg type. In contradistinction to normal GPA-M or -N, the N-terminal portion of GPA-Mg is not glycosylated. Therefore, the multipin peptide synthesis was used for testing the specificity of the cross-reacting MoAbs. Among several anti- M and anti-N MoAbs tested, only three anti-M (E3, E6, 425/2B) agglutinated Mg erythrocytes and showed binding to the synthetic octapeptides corresponding to N-terminal sequences of GPA-M (SSTTGVAM), GPA-N (LSTTEVAM), and GPA-Mg (LSTNEVAM). Testing multiple peptide analogs (window and replacement analysis) showed that these MoAbs were specific for peptidic epitope in which Met8 and Val6 were the most essential amino acid residues. The amino acid replacements Ser<-->Leu1 or Gly<-->Glu5 (M v N) and Thr<-->Asn4 (M and N v Mg) had no or negligible effect on the reaction of synthetic peptides with the MoAbs. However, when Ser2, Thr3, and Thr4 carry O-linked sialooligosaccharides (normal GPA-M or -N), the MoAbs recognize Gly5- and sialic acid- dependent blood group M-related epitope. An interesting finding concerning anti-M/Mg MoAbs described here is the fact that glycosylation of amino acid residues adjacent to the most important part of peptidic epitope not only differentially modulates the proper exposure of peptidic epitope, but also alters the requirement for some amino acid residues present within the epitope. Pathologic conditions, including hematologic disorders, are often accompanied by alterations in protein glycosylation, resulting not only from differences in the structure of antigen polypeptide chain, but also from changes in specificity or expression of enzymes involved in glycosylation. Our present findings draw attention to possibility of the bidirectional modulation of protein antigenicity by glycosylation and may be helpful in interpretation of some results obtained with MoAb used for diagnostic or other purposes.

The power of the force: mechano-physiology of the giant titin

2018 ◽  
Vol 2 (5) ◽  
pp. 681-686 ◽  
Author(s):  
Jaime Andrés Rivas-Pardo
Keyword(s):  
Amino Acid ◽  
Human Body ◽  
Actin Filaments ◽  
Polypeptide Chain ◽  
Single Gene ◽  
The Other ◽  
Amino Acid Residues ◽  
The Third ◽  
Single Polypeptide Chain ◽  
Single Polypeptide

Titin — the largest protein in the human body — spans half of the muscle sarcomere from the Z-disk to the M-band through a single polypeptide chain. More than 30 000 amino acid residues coded from a single gene (TTN, in humans Q8WZ42) form a long filamentous protein organized in individual globular domains concatenated in tandem. Owing to its location and close interaction with the other muscle filaments, titin is considered the third filament of muscle, after the thick-myosin and the thin-actin filaments.

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