scholarly journals Hydrogen ion equilibria in fish haemoglobins

1989 ◽  
Vol 143 (1) ◽  
pp. 225-234 ◽  
Author(s):  
F. B. Jensen
Keyword(s):  
Inverse Relationship ◽  
Structural Information ◽  
Amino Acid Sequences ◽  
Hydrogen Ion ◽  
Spiny Dogfish ◽  
Lower Content ◽  
Amino Groups ◽  
Histidine Residues ◽  
Fixed Acid ◽  
Haldane Effect

H+ titration studies on oxygenated and deoxygenated haemoglobins from carp, rainbow trout, spiny dogfish and pig are reported, and compared with Hb-H+ equilibria in other species and structural information deduced from amino acid sequences. The buffer values of oxygenated and deoxygenated teleost haemoglobins are low in comparison with elasmobranch and mammalian haemoglobins. This correlates with a much lower content of histidine residues and alpha-amino groups in teleost haemoglobins, than that in elasmobranch, dipnoan, amphibian, reptilian, avian and mammalian haemoglobins. The low total histidine content in teleost haemoglobins is paralleled by a reduced number of titratable histidine residues compared with that in mammals. An inverse relationship is observed between the magnitude of buffer values and the magnitude of fixed-acid Haldane effects. The largest Haldane effect and smallest buffer values are seen in carp, followed by trout, whereas the smallest Haldane effect and largest buffer values are seen in dogfish. The H+ equilibria of pig haemoglobin are intermediate between those of teleost and elasmobranch haemoglobins.

scholarly journals The Extracellular Transport Signal of the Vibrio cholerae Endochitinase (ChiA) Is a Structural Motif Located between Amino Acids 75 and 555

2002 ◽  
Vol 184 (8) ◽  
pp. 2225-2234 ◽  
Author(s):  
Jason P. Folster ◽  
Terry D. Connell
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Vibrio Cholerae ◽  
Structural Information ◽  
Amino Acid Sequences ◽  
Structural Motif ◽  
Terminal Branch ◽  
C Terminus ◽  
N Terminus ◽  
Extracellular Transport

ABSTRACT ChiA, an 88-kDa endochitinase encoded by the chiA gene of the gram-negative enteropathogen Vibrio cholerae, is secreted via the eps-encoded main terminal branch of the general secretory pathway (GSP), a mechanism which also transports cholera toxin. To localize the extracellular transport signal of ChiA that initiates transport of the protein through the GSP, a chimera comprised of ChiA fused at the N terminus with the maltose-binding protein (MalE) of Escherichia coli and fused at the C terminus with a 13-amino-acid epitope tag (E-tag) was expressed in strain 569B(chiA::Kanr), a chiA-deficient but secretion-competent mutant of V. cholerae. Fractionation studies revealed that blockage of the natural N terminus and C terminus of ChiA did not prevent secretion of the MalE-ChiA-E-tag chimera. To locate the amino acid sequences which encoded the transport signal, a series of truncations of ChiA were engineered. Secretion of the mutant polypeptides was curtailed only when ChiA was deleted from the N terminus beyond amino acid position 75 or from the C terminus beyond amino acid 555. A mutant ChiA comprised of only those amino acids was secreted by wild-type V. cholerae but not by an epsD mutant, establishing that amino acids 75 to 555 independently harbored sufficient structural information to promote secretion by the GSP of V. cholerae. Cys77 and Cys537, two cysteines located just within the termini of ChiA(75-555), were not required for secretion, indicating that those residues were not essential for maintaining the functional activity of the ChiA extracellular transport signal.

552. Heat-induced acidity in milk

1954 ◽  
Vol 21 (2) ◽  
pp. 207-211 ◽  
Author(s):  
F. H. Grimbleby
Keyword(s):  
Thermal Decomposition ◽  
Inverse Relationship ◽  
Titratable Acidity ◽  
Amino Groups

An inverse relationship has been demonstrated between the titratable acidity and formol titre of raw separated milk heated at temperatures of 60, 70 and 80° C. suggesting that the combination of lactose and protein, with the elimination of basic amino groups attached to protein, is one of the main reactions responsible for the heat-induced acidity. At temperatures of 90 and 100° C., when thermal decomposition of protein takes place, heat-induced acidity develops very rapidly and is accompanied by a marked increase in the number of basic amino groups and in the number of these groups which combine with lactose. Below 80° C. the development of acidity was not accompanied by discoloration of the millk, but at 80° C. and above, browning of the milk occurred. The relation between heat-induced acidity and browning is discussed.

scholarly journals An Integrative Database of β-Lactamase Enzymes: Sequences, Structures, Functions, and Phylogenetic Trees

2019 ◽  
Vol 63 (5) ◽  
Author(s):  
Vivek Keshri ◽  
Seydina M. Diene ◽  
Adrien Estienne ◽  
Justine Dardaillon ◽  
Olivier Chabrol ◽  
...  
Keyword(s):  
Phylogenetic Trees ◽  
Structural Information ◽  
Data Bank ◽  
Amino Acid Sequences ◽  
Medical Attention ◽  
Web Browsers ◽  
Structure Database ◽  
Primary Amino ◽  
Functional Profiles ◽  
Current Database

ABSTRACT β-Lactamase enzymes have attracted substential medical attention from researchers and clinicians because of their clinical, ecological, and evolutionary interest. Here, we present a comprehensive online database of β-lactamase enzymes. The current database is manually curated and incorporates the primary amino acid sequences, closest structural information in an external structure database (the Protein Data Bank [PDB]) and the functional profiles and phylogenetic trees of the four molecular classes (A, B, C, and D) of β-lactamases. The functional profiles are presented according to the MICs and kinetic parameters that make them more useful for the investigators. Here, a total of 1,147 β-lactam resistance genes are analyzed and described in the database. The database is implemented in MySQL and the related website is developed with Zend Framework 2 on an Apache server, supporting all major web browsers. Users can easily retrieve and visualize biologically important information using a set of efficient queries from a graphical interface. This database is freely accessible at http://ifr48.timone.univ-mrs.fr/beta-lactamase/public/.

Kinetic properties of the α-lytic protease of Sorangium sp., a bacterial homologue of the pancreatopeptidases

1969 ◽  
Vol 47 (3) ◽  
pp. 305-316 ◽  
Author(s):  
H. Kaplan ◽  
D. R. Whitaker
Keyword(s):  
Methyl Ester ◽  
Catalytic Properties ◽  
Substrate Binding ◽  
Kinetic Properties ◽  
Histidine Residue ◽  
Amino Groups ◽  
Binding Properties ◽  
Histidine Residues ◽  
Support Reaction ◽  
Hydrolysis Of

The kinetics under consideration are those of a bacterial serine protease with the same "active serine" sequence as chymotrypsin, trypsin, and elastase, and with a single histidine residue in a sequence which closely matches the sequences around histidine-57 of chymotrypsin and the analogous histidine residues of trypsin and elastase. In agreement with previous evidence of an elastase-like specificity, esters of N-substituted, neutral, aliphatic L-amino acids proved to be good to excellent substrates for the α-enzyme; esters of arginine, tyrosine, and tryptophan were not hydrolyzed. The enzyme has a much higher activity than the pancreatopeptidases towards p-nitrophenyl acetate and p-nitrophenyl trimethyl acetate; the catalytic rate coefficient kc for the latter substrate is about fivefold greater than that of elastase.The catalytic properties match those of the pancreatopeptidases in the following respects. As demonstrated with N-acetyl-L-valine methyl ester as substrate, kc is dependent on an ionization with a pKa of 6.7 in water and 7.3 in H22O; Δ log (kc/Km)/ΔpH for this ionization is equal to 1.0; kc is reduced 50% when H2O is replaced by H22O. These findings are consistent with a requirement for a single unprotonated histidine residue and general basic catalysis by that residue. The burst of p-nitrophenol in hydrolyses of p-nitrophenyl trimethyl acetate is proportional to [E]0; the magnitude of the proportionality factor and the rate of attainment of a steady state are consistent with the condition [Formula: see text], as in chymotrypsin kinetics. Thus the purely catalytic properties of the α-enzyme match those of chymotrypsin very closely. These findings do not support reaction mechanisms which require two catalytically functional histidine residues for such catalysis. The substrate-binding properties of the α-enzyme differ from those of chymotrypsin in that substrate binding does not depend on ionization of an N-terminal α-amino group; Km for the hydrolysis of N-acetyl-L-valine methyl ester is constant from pH 5 to pH 10 and enzymatic activity is unaffected by acetylation of the enzyme's α- and ε-amino groups. Ks for the hydrolysis of p-nitrophenyl trimethyl acetate is appreciably greater than the Ks of elastase for this substrate.The chloromethyl ketones of glycine and valine did not inhibit the enzyme or alkylate its histidine residue.

scholarly journals ThermoMutDB: a thermodynamic database for missense mutations

2020 ◽  
Vol 49 (D1) ◽  
pp. D475-D479
Author(s):  
Joicymara S Xavier ◽  
Thanh-Binh Nguyen ◽  
Malancha Karmarkar ◽  
Stephanie Portelli ◽  
Pâmela M Rezende ◽  
...  
Keyword(s):  
Structural Information ◽  
Amino Acid Sequences ◽  
Missense Mutations ◽  
Mutant Proteins ◽  
Manual Curation ◽  
Data Points ◽  
Dynamic Structures ◽  
Further Development ◽  
Programmatic Access ◽  
Annotation Errors

Abstract Proteins are intricate, dynamic structures, and small changes in their amino acid sequences can lead to large effects on their folding, stability and dynamics. To facilitate the further development and evaluation of methods to predict these changes, we have developed ThermoMutDB, a manually curated database containing >14,669 experimental data of thermodynamic parameters for wild type and mutant proteins. This represents an increase of 83% in unique mutations over previous databases and includes thermodynamic information on 204 new proteins. During manual curation we have also corrected annotation errors in previously curated entries. Associated with each entry, we have included information on the unfolding Gibbs free energy and melting temperature change, and have associated entries with available experimental structural information. ThermoMutDB supports users to contribute to new data points and programmatic access to the database via a RESTful API. ThermoMutDB is freely available at: http://biosig.unimelb.edu.au/thermomutdb.

Hydrogen ion titrations of the anodic and cathodic haemoglobin components of the European eel Anguilla anguilla.

1998 ◽  
Vol 201 (17) ◽  
pp. 2507-2514 ◽  
Author(s):  
C J Brauner ◽  
R E Weber
Keyword(s):  
Anguilla Anguilla ◽  
Molar Ratio ◽  
European Eel ◽  
Ph Homeostasis ◽  
Histidine Residues ◽  
Ph Values ◽  
Buffer Value ◽  
Ph Range ◽  
Haldane Effect

H+ titrations were conducted on the separated haemoglobin components of eel Anguilla anguilla in both the oxygenated and deoxygenated states. In anodic haemoglobin, the addition of GTP, and to a lesser extent C1-, increased the magnitude of the Haldane effect and shifted its maximum value into the in vivo pH range. Of the 22 histidine residues in the anodic component, only approximately seven were titratable, presumably the beta-chain residues at positions 41, 97, 109 and 146 (helical positions C7, FG4, G11 and HC3, respectively). In cathodic haemoglobin, a small negative Haldane effect was observed at pH values between 6.8 and 8.5 which disappeared in the presence of GTP (molar ratio 3:1 GTP:haemoglobin tetramer). GTP had virtually no effect on the buffer value at fixed oxygenation status, and the lowest buffer value was observed at in vivo pH values. No titratable histidine residues were observed in the cathodic component, indicating that all 14 histidines in this component are buried. We conclude that the anodic component, which constitutes two-thirds of the haemoglobin in the eel, plays the predominant role in CO2 transport and pH homeostasis in vivo.

Haemoglobin H+ equilibria in lamprey (Lampetra fluviatilis) and hagfish (Myxine glutinosa)

1999 ◽  
Vol 202 (14) ◽  
pp. 1963-1968
Author(s):  
F.B. Jensen
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Carrying Capacity ◽  
Venous Blood ◽  
Evolutionary Divergence ◽  
High Concentration ◽  
High Co2 ◽  
Virtual Absence ◽  
Fixed Acid ◽  
Haldane Effect

Agnathans, comprising lamprey and hagfish species, have been reported to be practically devoid of HCO3-/Cl- exchange across the red blood cell membrane. This suggests that the capacity of their haemoglobin (Hb) to remove H+ is essential for obtaining a high CO2-carrying capacity in the blood. Hydrogen ion titrations were performed on oxygenated and deoxygenated composite Hbs from river lamprey and from Atlantic hagfish at 15 degrees C and an ionic strength of 0.1 (0.1 mol l-1 KCl). Lamprey Hb was characterised by very low buffer values when the degree of oxygenation was constant, whereas the fixed-acid Haldane effect was large (uptake of approximately 0.9 H+ per monomer upon deoxygenation). Hagfish Hb, in contrast, had large buffer values and a moderate fixed-acid Haldane effect. In deoxygenated Hb, the low buffer values in lamprey correlated with the presence of only 1–1.5 titratable ‘neutral’ groups (normally histidines and α -amino groups) per monomer, whereas there were 4–5 titratable ‘neutral’ groups per monomer in hagfish. The large differences in Hb/H+ equilibria between the two species reflect the early evolutionary divergence between lampreys and hagfish. With respect to CO2 transport, the special Hb/H+ equilibria and the high red blood cell pH in lamprey ensure a high concentration of free HCO3- inside the red cells in venous blood, which compensates for the absence of a shift of HCO3- to the plasma. The Hb/H+ equilibria in hagfish are less effective in ensuring a high CO2-carrying capacity given the virtual absence of a red blood cell HCO3-/Cl- exchange, and other adaptations may be involved.

BINDING OF ZINC TO INSULIN AND SOME INSULIN DERIVATIVES STUDIED BY PAPER ELECTROPHORESIS

1969 ◽  
Vol 61 (3) ◽  
pp. 561-576 ◽  
Author(s):  
K. Brunfeldt ◽  
B. A. Hansen ◽  
J. Hoiriis Nielsen
Keyword(s):  
Binding Capacity ◽  
Fluorescein Isothiocyanate ◽  
Paper Electrophoresis ◽  
Zinc Binding ◽  
Amino Groups ◽  
Histidine Residues ◽  
Tyrosine Residues ◽  
Barbital Buffer ◽  
Pronounced Reduction ◽  
Electrophoretic Fractionation

ABSTRACT Paper electrophoretic fractionation in barbiturate (barbital) buffer, pH 9, of iodine-substituted insulin 0–10.8 I/mole showed that substitution with 4–6 I/mole influences the binding of zinc to a demonstrable extent. The effect appears to be due to substitution in the imidazole groups of the histidine residues. Substitution with iodine in the tyrosine residues seems to be without significance, at least at the lower degrees of iodination. The importance of the histidine residues for the binding of zinc is shown by selective destruction of the imidazole groups by photo-oxidation, sensitized by methylene blue. Carbamylation of the N-terminal α-amino groups in the A- and B-chains with KOCN only slightly influences the ability to bind zinc while carbamylation with fluorescein isothiocyanate in the N-terminal of the B-chain brings about a more pronounced reduction in the zinc binding capacity.

Characterization of the topology and functional domains of RKTG

2008 ◽  
Vol 414 (3) ◽  
pp. 399-406 ◽  
Author(s):  
Xiaolin Luo ◽  
Lin Feng ◽  
Xiaomeng Jiang ◽  
Fei Xiao ◽  
Zhenzhen Wang ◽  
...  
Keyword(s):  
Golgi Apparatus ◽  
Structural Information ◽  
Transmembrane Protein ◽  
Cell Signalling ◽  
Amino Acid Sequences ◽  
Transmembrane Domains ◽  
Functional Domains ◽  
Golgi Localization ◽  
N Terminus

RKTG (Raf kinase trapping to Golgi) is exclusively localized at the Golgi apparatus and functions as a spatial regulator of Raf-1 kinase by sequestrating Raf-1 to the Golgi. Based on the structural similarity with adiponectin receptors, RKTG was predicted to be a seven-transmembrane protein with a cytosolic N-terminus, distinct from classical GPCRs (G-protein-coupled receptors). We analysed in detail the topology and functional domains of RKTG in this study. We determined that the N-terminus of RKTG is localized on the cytosolic side. Two short stretches of amino acid sequences at the membrane proximal to the N- and C-termini (amino acids 61–71 and 299–303 respectively) were indispensable for Golgi localization of RKTG, but were not required for the interaction with Raf-1. The three loops facing the cytosol between the transmembrane domains had different roles in Golgi localization and Raf-1 interaction. While the first cytosolic loop was only important for Golgi localization, the third cytosolic loop was necessary for both Golgi localization and Raf-1 sequestration. Taken together, these findings suggest that RKTG is a type III membrane protein with its N-terminus facing the cytosol and multiple sequences are responsible for its localization at the Golgi apparatus and Raf-1 interaction. As RKTG is the first discovered Golgi protein with seven transmembrane domains, the knowledge derived from this study would not only provide structural information about the protein, but also pave the way for future characterization of the unique functions of RKTG in the regulation of cell signalling.

Sign in / Sign up

Export Citation Format

Share Document