scholarly journals Slow conformational changes of a Neurospora glutamate dehydrogenase studied by protein fluorescence

1974 ◽  
Vol 143 (2) ◽  
pp. 317-329 ◽  
Author(s):  
Barrie Ashby ◽  
John C. Wootton ◽  
John R. S. Fincham
Keyword(s):  
Glutamate Dehydrogenase ◽  
Conformational Change ◽  
Conformational Changes ◽  
Fluorescence Emission ◽  
Enzyme Activation ◽  
Protein Fluorescence ◽  
Fluorescence Emission Spectra ◽  
Iodide Ions ◽  
Inactive State ◽  
Ph Values

1. The NADP-dependent glutamate dehydrogenase of Neurospora crassa undergoes slow reversible structural transitions, with half-times in the order of a few minutes, between active and inactive states. The inactive state of the enzyme, which predominates at pH values below 7.0, has an intrinsic tryptophan fluorescence 25% lower than that of the active state, which predominates at pH values above 7.6. The inactive state can be activated either by an increase in pH or by addition of activators such as succinate. 2. The kinetics of the slow transitions that follow activating and inactivating rapid changes in conditions have been monitored by measurements of protein fluorescence. The results show that the slow reversible conformational change detected by the change in fluorescence is the rate-limiting process for enzyme activation and inactivation. 3. In both directions this conformational change follows apparent first-order kinetics and the rate constant is independent of protein concentration. These kinetics and published measurements of molecular weight are indicative of an isomerization process. 4. In both directions the changes show a large energy of activation and a large positive entropy of activation, consistent with a considerable disturbance of conformation in the transition state. 5. Comparisons of the fluorescence emission spectra of the active and inactive states indicate that the difference in fluorescence is produced by quenching, possibly intramolecular, in the inactive conformation. Iodide ions cause similar quenching. 6. In some mutationally altered forms of the enzyme comparable but modified conformational changes can be followed by protein fluorescence.

scholarly journals Positive co-operative binding at two weak lysine-binding sites governs the Glu-plasminogen conformational change

1992 ◽  
Vol 285 (2) ◽  
pp. 419-425 ◽  
Author(s):  
U Christensen ◽  
L Mølgaard
Keyword(s):  
Ligand Binding ◽  
Binding Site ◽  
Conformational Change ◽  
Conformational Changes ◽  
Binding Sites ◽  
High Specificity ◽  
Stopped Flow ◽  
Protein Fluorescence ◽  
Lysine Residues ◽  
Kinetics Of

The kinetics of a series of Glu-plasminogen ligand-binding processes were investigated at pH 7.8 and 25 degrees C (in 0.1 M-NaCl). The ligands include compounds analogous to C-terminal lysine residues and to normal lysine residues. Changes of the Glu-plasminogen protein fluorescence were measured in a stopped-flow instrument as a function of time after rapid mixing of Glu-plasminogen and ligand at various concentrations. Large positive fluorescence changes (approximately 10%) accompany the ligand-induced conformational changes of Glu-plasminogen resulting from binding at weak lysine-binding sites. Detailed studies of the concentration-dependencies of the equilibrium signals and the rate constants of the process induced by various ligands showed the conformational change to involve two sites in a concerted positive co-operative process with three steps: (i) binding of a ligand at a very weak lysine-binding site that preferentially, but not exclusively, binds C-terminal-type lysine ligands, (ii) the rate-determining actual-conformational-change step and (iii) binding of one more lysine ligand at a second weak lysine-binding site that then binds the ligand more tightly. Further, totally independent initial small negative fluorescence changes (approximately 2-4%) corresponding to binding at the strong lysine-binding site of kringle 1 [Sottrup-Jensen, Claeys, Zajdel, Petersen & Magnusson (1978) Prog. Chem. Fibrinolysis Thrombolysis 3, 191-209] were observed for the C-terminal-type ligands. The finding that the conformational change in Glu-plasminogen involves two weak lysine-binding sites indicates that the effect cannot be assigned to any single kringle and that the problem of whether kringle 4 or kringle 5 is responsible for the process resolves itself. Probably kringle 4 and 5 are both participating. The involvement of two lysine binding-sites further makes the high specificity of Glu-plasminogen effectors more conceivable.

scholarly journals The conformational changes of α2-macroglobulin induced by methylamine or trypsin. Characterization by extrinsic and intrinsic spectroscopic probes

1987 ◽  
Vol 243 (1) ◽  
pp. 47-54 ◽  
Author(s):  
L J Larsson ◽  
P Lindahl ◽  
C Hallén-Sandgren ◽  
I Björk
Keyword(s):  
Conformational Change ◽  
Conformational Changes ◽  
Fluorescence Emission ◽  
Tryptophan Fluorescence ◽  
Cross Linking ◽  
Bait Region ◽  
Close Proximity ◽  
Tryptophan Residues ◽  
Thioester Bond ◽  
Bond Region

The conformational changes around the thioester-bond region of human or bovine alpha 2M (alpha 2-macroglobulin) on reaction with methylamine or trypsin were studied with the probe AEDANS [N-(acetylaminoethyl)-8-naphthylamine-1-sulphonic acid], bound to the liberated thiol groups. The binding affected the fluorescence emission and lifetime of the probe in a manner indicating that the thioester-bond region is partially buried in all forms of the inhibitor. In human alpha 2M these effects were greater for the trypsin-treated than for the methylamine-treated inhibitor, which both have undergone similar, major, conformational changes. This difference may thus be due to a close proximity of the thioester region to the bound proteinase. Reaction of trypsin with thiol-labelled methylamine-treated bovine alpha 2M, which retains a near-native conformation and inhibitory activity, indicated that the major conformational change accompanying the binding of proteinases involves transfer of the thioester-bond region to a more polar environment without increasing the exposure of this region at the surface of the protein. Labelling of the transglutaminase cross-linking site of human alpha 2M with dansylcadaverine [N-(5-aminopentyl)-5-dimethylaminonaphthalene-1-sulphonamide] suggested that this site is in moderately hydrophobic surroundings. Reaction of the labelled inhibitor with methylamine or trypsin produced fluorescence changes consistent with further burial of the cross-linking site. These changes were more pronounced for trypsin-treated than for methylamine-treated alpha 2M, presumably an effect of the cleavage of the adjacent ‘bait’ region. Solvent perturbation of the u.v. absorption and iodide quenching of the tryptophan fluorescence of human alpha 2M showed that one or two tryptophan residues in each alpha 2M monomer are buried on reaction with methylamine or trypsin, with no discernible change in the exposure of tyrosine residues. Together, these results indicate an extensive conformational change of alpha 2M on reaction with amines or proteinases and are consistent with several aspects of a recently proposed model of alpha 2M structure [Feldman, Gonias & Pizzo (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 5700-5704].

scholarly journals Allosteric regulation: Illuminating allosteric conformational change with an environmentally sensitive fluorescent probe

2015 ◽  
Vol 37 (3) ◽  
pp. 54-57
Author(s):  
Robert B. Freedman ◽  
Alan D.B. Malcolm
Keyword(s):  
Glutamate Dehydrogenase ◽  
Fluorescent Probe ◽  
Conformational Change ◽  
Conformational Changes ◽  
Allosteric Regulation ◽  
Structural Data ◽  
Biochemical Journal ◽  
Environmentally Sensitive ◽  
The 1960S ◽  
Classic Paper

Allosteric regulation was a hot topic in the 1960s, but there was very limited structural data on allosteric equilibria, and no solid information on the rates of allosteric conformational changes. In this Biochemical Journal Classic paper from 1969 George Radda and his first D.Phil. student, George Dodd determined the rate of allosteric transition in the regulatory enzyme glutamate dehydrogenase by a method new in the 1960s, the fluorescence of an environmentally sensitive extrinsic probe.

Possible mechanism for the inhibition of lectin-erythrocyte interaction in presence of endogenous lectin receptor

1996 ◽  
Vol 16 (6) ◽  
pp. 453-458
Author(s):  
Prabnab S. Basu ◽  
Pradip K. Datta ◽  
Tapash K. Datta
Keyword(s):  
Conformational Changes ◽  
Sulfonic Acid ◽  
Hydrophobic Interactions ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Hydrophobic Region ◽  
Fluorescence Emission Spectra ◽  
Lectin Receptor ◽  
Endogenous Lectin ◽  
Group A

The presence of hydrophobic sites in the lectin-I molecule was indicated by hydrophobic probes like 1-anilinonapthalene-8-sulfonic acid (ANS), 2-p-toluidinyl napthalene-6-sulfonic acid (TNS), N-phenyl-1-napthylamine (NA) and rose bengal (RB). This was further confirmed by amino acid modifications in the hydrophobic region of the lectin-I molecule. The binding of ANS, TNS, NA and RB to lectin-I was affected in the presence of NaCl. The involvement of hydrophobic interactions in rice-bean lectin-I-endogenous lectin receptor (ELR) complex were indicated by alterations in the circular dichroism and fluorescence emission spectra. The percentage of β-conformation (55–63%) of lectin-I was decreased by addition of ELR. ELR on reacting with lectin-I reduced the fluorescence emissions of the hydrophobic probes while fluorescence emission of ANS, TNS, NA and RB were greatly enhanced in presence of lectin-I alone. N-aceyl-galactosamine did not change the fluorescence emissions of any of the hydrophobic probes in presence or in absence of lectin-I. This demonstrates that carbohydrate and hydrophobic sites may be different and non-interacting. It is proposed that the ELR in reacting with lectin-I, induced conformational changes in the lectin-I molecule and thereby affected its erythroagglutinating activity with human blood group “A” erythrocytes.

scholarly journals Conformational studies on phospholipase C from Bacillus cereus. The effect of urea on the enzyme

1978 ◽  
Vol 175 (3) ◽  
pp. 977-986 ◽  
Author(s):  
C Little
Keyword(s):  
Circular Dichroism ◽  
Bacillus Cereus ◽  
Phospholipase C ◽  
Thermal Inactivation ◽  
Elevated Temperatures ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Protein Fluorescence ◽  
Fluorescence Emission Spectra ◽  
Circular Dichroïsm

1. When heated in 8 M-urea, phospholipase C(EC 3.1.4.3) from Bacillus cereus undergoes conformational transitions depending on the temperatures used. These transitions were studied by examining protein fluorescence, iodide quenching of protein fluorescence, u.v. difference spectroscopy, chemical availability of histidine residues in the enzyme, circular dichroism and catalytic activity. 2. Unless simultaneously exposed to elevated temperatures the enzyme appears to be unaffected by 8 M-urea. Removal of the two zinc atoms from the enzyme renders phospholipase C very sensitive to denaturation by 8 M-urea as indicated by fluorescence emission spectra and circular dichroism. 3. Both the native and the zinc-free enzymes are markedly more resistant to irreversible thermal inactivation in the presence of 8 M-urea than in its absence. 4. The response of the enzyme to 8 M-urea and the role of zinc in stabilizing the enzyme are discussed.

scholarly journals Biomolecular condensates amplify mRNA decapping by coupling protein interactions with conformational changes in Dcp1/Dcp2

2020 ◽  
Author(s):  
Ryan W. Tibble ◽  
Anaïs Depaix ◽  
Joanna Kowalska ◽  
Jacek Jemielity ◽  
John D. Gross
Keyword(s):  
Conformational Change ◽  
Conformational Changes ◽  
Protein Interactions ◽  
Mrna Degradation ◽  
Enzyme Activation ◽  
List Type ◽  
Protein Protein Interactions ◽  
Mrna Decapping ◽  
P Bodies

SUMMARYCells organize biochemical processes into biological condensates. P-bodies are cytoplasmic condensates enriched in factors important for mRNA degradation. P-bodies have been identified as sites of both mRNA storage and decay, but how these opposing outcomes may be achieved in condensates is unresolved. A critical step in mRNA degradation is removal of the 5’-7-methylguanosine cap by Dcp1/Dcp2, which is highly enriched in P-bodies. Dcp1/Dcp2 activity is repressed in condensates in vitro and requires the activator Edc3. Activation of decapping is amplified in condensates relative to the surrounding solution due to stabilization of an autoinhibited state in Dcp1/Dcp2. Edc3 couples a conformational change in the Dcp1/Dcp2 active site with alteration of the protein-protein interactions driving phase separation to activate decapping in condensates. The composition-dependent regulation of enzyme activity in condensates occurs over length scales ranging from microns to Ångstroms and may control the functional state of P-bodies and related phase-separated compartments.HIGHLIGHTSmRNA decapping in droplets is repressedCatalytically inert droplets are activated by a change in condensate compositionA switch in enzymatic activity requires a conformational change in condensatesCondensates amplify enzyme activation compared to surrounding solution

scholarly journals Interaction of Zn2+ and Eu3+ with bovine liver glutamate dehydrogenase

1987 ◽  
Vol 246 (1) ◽  
pp. 199-203 ◽  
Author(s):  
E T Bell ◽  
A M Stilwell ◽  
J E Bell
Keyword(s):  
Binding Site ◽  
Glutamate Dehydrogenase ◽  
Quaternary Structure ◽  
Resonance Energy Transfer ◽  
Fluorescence Emission ◽  
Resonance Energy ◽  
Bovine Liver ◽  
Heat Stability ◽  
Protein Fluorescence ◽  
Excitation Peak

Bovine liver glutamate dehydrogenase is potently inhibited by Zn2+ ions. At pH 7.0 a kinetic dissociation constant for Zn2+ of 18 microM is obtained. The fluorescent lanthanide Eu3+ competes for the Zn2+-binding site and relieves the Zn2+-induced inhibition, but does not cause inhibition. Studies on the effects of Zn2+ or Eu3+ on the tertiary and quaternary structure of the enzyme by the use of protein fluorescence, heat-stability and re-activation after guanidinium chloride denaturation indicate that, whereas Zn2+ affects both tertiary and quaternary structure, Eu3+ does not affect either, consistent with its lack of effect on enzymic properties. Eu3+ fluorescence had a strong excitation peak at 395 nm with emission at 456 nm. In the presence of glutamate dehydrogenase the fluorescence emission is shifted to 501 nm. Eu3+, with high-affinity binding site and distinctive fluorescence properties after binding, would appear to be an ideal fluorophore for use in conformational studies or resonance-energy-transfer studies.

scholarly journals Influence of Gamma Irradiation on Porcine Serum Albumin Structural Properties and Allergenicity

2018 ◽  
Vol 101 (2) ◽  
pp. 529-535
Author(s):  
Xudong Zhu ◽  
Wei Wang ◽  
Juan Shen ◽  
Xinglian Xu ◽  
Guanghong Zhou
Keyword(s):  
Serum Albumin ◽  
Gamma Irradiation ◽  
Conformational Changes ◽  
Immunoglobulin E ◽  
Fluorescence Emission ◽  
Sulfhydryl Group ◽  
Fluorescence Emission Spectra ◽  
Porcine Serum ◽  
Gamma Irradiated ◽  
The Impact

Abstract Pork provides an ideal source of food energy; however, pork can elicit an allergic reaction, and porcine serum albumin (PSA) has been identified as a major allergen. This study examined the impact of gamma irradiation on the allergenicity and structural qualities of PSA; the PSA solution was gamma-irradiated at 1, 2, 4, 6, and 8 kGy. Allergenicity was investigated by immunoblotting and competitive indirect ELISA using serum from patients who are allergic to pork, and conformational changes in irradiated PSA were measured by circular dichroism, sulfhydryl group detection, and fluorescence emission spectra. The secondary and tertiary structures of gamma-irradiated PSA were altered, and the allergenicity of PSA was lowered by boosting the amount of irradiation. In addition, there is high correlation between depletion in the α-helix and immunoglobulin E-binding capability of PSA. The results show a new possibility in using gamma irradiation to reduce the allergenicity of pork products.

scholarly journals Cloning and expression of a cDNA encoding a new neurocalcin isoform (neurocalcin α) from bovine brain

1998 ◽  
Vol 331 (3) ◽  
pp. 871-876 ◽  
Author(s):  
Masumi KATO ◽  
Yasuo WATANABE ◽  
Satoshi IINO ◽  
Yuri TAKAOKA ◽  
Shigeru KOBAYASHI ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Immunohistochemical Analysis ◽  
Bovine Brain ◽  
Cloning And Expression ◽  
Mobility Shift ◽  
Fluorescence Emission Spectra ◽  
Neuronal Tissues ◽  
Neuron Function

Neurocalcin (NC), a neuron-specific EF-hand Ca2+-binding protein, purified from bovine brain [Terasawa, Nakano, Kobayashi and Hidaka (1992) J. Biol. Chem. 267, 19596–19599] contains multiple isoforms. We previously cloned NCδ from bovine brain and showed high expression in neuronal tissues [Okazaki, Watanabe, Ando, Hagiwara, Terasawa and Hidaka (1992) Biochem. Biophys. Res. Commun. 185, 147–153]. We report here the molecular cloning and expression of a cDNA encoding bovine brain NCα. The translated bovine protein is 191 amino acids long and shares 69.1% of its amino acid sequence with NCδ. Recombinant NCα migrates as a single 23 kDa band and exhibits a Ca2+-dependent mobility shift on SDS/PAGE. Analysis of fluorescence emission spectra showed the Ca2+-induced peak at 337 nm. Interestingly, the mobility shift and the fluorescence intensity at 337 nm were larger for NCα than for NCδ. In Ca2+-overlay experiments, however, the apparent affinity of NCα for 45Ca2+ was similar to that of NCδ. Immunohistochemical analysis revealed NCα expression in the granular layer of the rat cerebellar cortex whereas NCδ was found in the Purkinje cell layer. In the rat olfactory bulb, NCα was located in external tufted cells, and NCδ was found in the periglomerular cells. These data demonstrate that NC isoforms differ in their tissue distribution and conformational changes induced by Ca2+ binding. Thus differential regulation of the two NC isoforms may be involved in control of neuron function.

Optical Properties and Zinc Nitride Thin Films Prepared Using Magnetron Reactive Sputtering

2014 ◽  
Vol 940 ◽  
pp. 11-15
Author(s):  
Jun Qin Feng ◽  
Jun Fang Chen
Keyword(s):  
Thin Films ◽  
Band Gap ◽  
Near Infrared ◽  
Fluorescence Emission ◽  
Emission Spectra ◽  
Sem Images ◽  
Fluorescence Emission Spectra ◽  
Glass Substrates ◽  
Zinc Nitride ◽  
Direct Band

Zinc nitride films were deposited by ion sources-assisted magnetron sputtering with the use of Zn target (99.99% purity) on 7059 glass substrates. The films were characterized by XRD, SEM and EDS, the results of which show that the polycrystalline zinc nitride thin film can be grown on the glass substrates, the EDS spectrum confirmed the chemical composition of the films and the SEM images revealed that the zinc nitride thin films have a dense structure. Ultraviolet-visible-near infrared spectrophotometer was used to study the transmittance behaviors of zinc nitride thin films, which calculated the optical band gap by Davis Mott model. The results of the fluorescence emission spectra show the zinc nitride would be a direct band gap semiconductor material.

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