scholarly journals Kinetic and thermodynamic consequences of the removal of theCys-77–Cys-123 disulphide bond for the folding of TEM-1 β-lactamase

1997 ◽  
Vol 321 (2) ◽  
pp. 413-417 ◽  
Author(s):  
Marc VANHOVE ◽  
Gilliane GUILLAUME ◽  
Philippe LEDENT ◽  
John H. RICHARDS ◽  
Roger H. PAIN ◽  
...  
Keyword(s):  
Thermal Inactivation ◽  
Guanidine Hydrochloride ◽  
Tryptophan Fluorescence ◽  
Disulphide Bond ◽  
Mutant Protein ◽  
Wild Type ◽  
High Concentration ◽  
Proline Isomerization ◽  
Drastic Increase ◽  
Time Courses

Class A α-lactamases of the TEM family contain a single disulphide bond which connects cysteine residues 77 and 123. To clarify the possible role of the disulphide bond in the stability and folding kinetics of the TEM-1 α-lactamase, this bond was removed by introducing a Cys-77 → Ser mutation, and the enzymically active mutant protein was studied by reversible guanidine hydrochloride-induced denaturation. The unfolding and refolding rates were monitored using tryptophan fluorescence. At low guanidine hydrochloride concentrations, the refolding of the wild-type and mutant enzymes followed biphasic time courses. The characteristics of the two phases were not significantly affected by the mutation. Double-jump experiments, in which the protein was unfolded in a high concentration of guanidine hydrochloride for a short time period and then refolded by diluting out the denaturant, indicated that, for both the wild-type and mutant enzymes, the two refolding phases could be ascribed to proline isomerization reactions. Equilibrium unfolding experiments monitored by fluorescence spectroscopy and far-UV CD indicated a three-state mechanism (N ↔ H ↔ U). Both the folded mutant protein (N) and, to a lesser extent, the thermodynamically stable intermediate, H, were destabilized relative to the fully unfolded state, U. Removal of the disulphide bond resulted in a decrease of 14.2 kJ/mol (3.4 kcal/mol) in the global free energy of stabilization. Similarly, the mutation also induced a drastic increase in the rate of thermal inactivation.

scholarly journals Phe71Is Essential for Chaperone-like Function in αA-crystallin

2001 ◽  
Vol 276 (50) ◽  
pp. 47094-47099 ◽  
Author(s):  
Puttur Santhoshkumar ◽  
K. Krishna Sharma
Keyword(s):  
Tertiary Structure ◽  
Citrate Synthase ◽  
Molecular Size ◽  
Tryptophan Fluorescence ◽  
Site Directed Mutagenesis ◽  
Mutant Protein ◽  
Disulfonic Acid ◽  
Wild Type ◽  
Mutant Proteins ◽  
Structural And Functional Properties

Experiments with mini-αA-crystallin (KFVIFLDVKHFSPEDLTVK) showed that Phe71in αA-crystallin could be essential for the chaperone-like action of the protein (Sharma, K. K., Kumar, R. S., Kumar, G. S., and Quinn, P. T. (2000)J. Biol. Chem.275, 3767–3771). In the present study we replaced Phe71in rat αA-crystallin with Gly by site-directed mutagenesis and then compared the structural and functional properties of the mutant protein with the wild-type protein. There were no differences in molecular size or intrinsic tryptophan fluorescence between the proteins. However, 1,1′-bi(4-anilino)naphthalene-5,5′-disulfonic acid interaction indicated a higher hydrophobicity for the mutant protein. Both wild-type and mutant proteins displayed similar secondary structure during far UV CD experiments. Near UV CD signal showed a slight difference in the tertiary structure around the 285–295 region for the two proteins. The mutant protein was totally inactive in suppressing the aggregation of reduced insulin, heat-denatured citrate synthase, and alcohol dehydrogenase. However, a marginal suppression of βL-crystallin aggregation was observed when mutant αA-crystallin was included. These results suggest that Phe71contributes to the chaperone-like action of αA-crystallin. Therefore we conclude that the 70–88-region in αA-crystallin, identified by us earlier, is the functional chaperone site in αA-crystallin.

scholarly journals Isolation of omnipotent suppressors in an [eta+] yeast strain.

Genetics ◽  
1990 ◽  
Vol 124 (3) ◽  
pp. 505-514 ◽  
Author(s):  
J A All-Robyn ◽  
D Kelley-Geraghty ◽  
E Griffin ◽  
N Brown ◽  
S W Liebman
Keyword(s):  
Yeast Strain ◽  
Guanidine Hydrochloride ◽  
Wild Type ◽  
Translational Fidelity ◽  
Genetic Analyses ◽  
Mendelian Factor ◽  
Nonsense Codons

Abstract Omnipotent suppressors decrease translational fidelity and cause misreading of nonsense codons. In the presence of the non-Mendelian factor [eta+], some alleles of previously isolated omnipotent suppressors are lethal. Thus the current search was conducted in an [eta+] strain in an effort to identify new suppressor loci. A new omnipotent suppressor, SUP39, and alleles of sup35, sup45, SUP44 and SUP46 were identified. Efficiencies of the dominant suppressors were dramatically reduced in strains that were cured of non-Mendelian factors by growth on guanidine hydrochloride. Wild-type alleles of SUP44 and SUP46 were cloned and these clones were used to facilitate the genetic analyses. SUP44 was shown to be on chromosome VII linked to cyh2, and SUP46 was clearly identified as distinct from the linked sup45.

scholarly journals Activation of Kinin B1R Upregulates ADAM17 and Results in ACE2 Shedding in Neurons

2020 ◽  
Vol 22 (1) ◽  
pp. 145
Author(s):  
Rohan Umesh Parekh ◽  
Srinivas Sriramula
Keyword(s):  
Protein Expression ◽  
Renin Angiotensin System ◽  
Neuronal Cultures ◽  
Wild Type ◽  
High Concentration ◽  
Neurogenic Hypertension ◽  
B1 Receptor ◽  
Gene And Protein Expression ◽  
Kinin B1 Receptor ◽  
Specific Antagonist

Angiotensin converting enzyme 2 (ACE2) is a critical component of the compensatory axis of the renin angiotensin system. Alterations in ACE2 gene and protein expression, and activity mediated by A Disintegrin And Metalloprotease 17 (ADAM17), a member of the “A Disintegrin And Metalloprotease” (ADAM) family are implicated in several cardiovascular and neurodegenerative diseases. We previously reported that activation of kinin B1 receptor (B1R) in the brain increases neuroinflammation, oxidative stress and sympathoexcitation, leading to the development of neurogenic hypertension. We also showed evidence for ADAM17-mediated ACE2 shedding in neurons. However, whether kinin B1 receptor (B1R) activation has any role in altering ADAM17 activity and its effect on ACE2 shedding in neurons is not known. In this study, we tested the hypothesis that activation of B1R upregulates ADAM17 and results in ACE2 shedding in neurons. To test this hypothesis, we stimulated wild-type and B1R gene-deleted mouse neonatal primary hypothalamic neuronal cultures with a B1R-specific agonist and measured the activities of ADAM17 and ACE2 in neurons. B1R stimulation significantly increased ADAM17 activity and decreased ACE2 activity in wild-type neurons, while pretreatment with a B1R-specific antagonist, R715, reversed these changes. Stimulation with specific B1R agonist Lys-Des-Arg9-Bradykinin (LDABK) did not show any effect on ADAM17 or ACE2 activities in neurons with B1R gene deletion. These data suggest that B1R activation results in ADAM17-mediated ACE2 shedding in primary hypothalamic neurons. In addition, stimulation with high concentration of glutamate significantly increased B1R gene and protein expression, along with increased ADAM17 and decreased ACE2 activities in wild-type neurons. Pretreatment with B1R-specific antagonist R715 reversed these glutamate-induced effects suggesting that indeed B1R is involved in glutamate-mediated upregulation of ADAM17 activity and ACE2 shedding.

A structure—function study of dihydrofolate reductase by protein engineering

1986 ◽  
Vol 317 (1540) ◽  
pp. 405-413 ◽  
Keyword(s):  
Structure Function ◽  
Dihydrofolate Reductase ◽  
Conformational Changes ◽  
Guanidine Hydrochloride ◽  
Disulphide Bond ◽  
E Coli ◽  
Transition State Stabilization ◽  
Disulphide Bond Formation ◽  
High Resolution Structure ◽  
Charge Interaction

Several mutants of the enzyme dihydrofolate reductase (DHFR) have been engineered by oligonucleotide-directed mutagenesis of the cloned E. coli gene. The mutations were designed to address specific questions about DHFR structure-function relations that arose from the analysis of the high-resolution structure. Mutations at the active site have revealed that the invariant residue aspartate-27 is involved in substrate protonation, and not in transition-state stabilization as previously thought. The 2.0 Å (1 Å = 10 -1 nm = 10 -10 m) refined structures of the Asn-27 and Ser-27 mutant enzymes reveal that the enhanced binding observed for the 2,4-diamino pteridine and pyrimidine inhibitors is probably not attributable to the charge interaction between Asp-27 and a protonated N-1 of the inhibitor. Substitution of a cysteine for a proline at position 39 places two sulphydryls within bonding distance, and under certain oxidation conditions they will quantitatively form a disulphide bond. The refined 2.0 Å structures of both reduced and oxidized forms of this mutant show that only minor conformational changes occur for disulphide bond formation. The crosslinked enzyme is significantly more conformationally stable to denaturants such as guanidine hydrochloride and urea.

scholarly journals Effect of Structural Changes Induced by Deletion of 54FLRAPSWF61 Sequence in αB-Crystallin on Chaperone Function and Anti-Apoptotic Activity

2021 ◽  
Vol 22 (19) ◽  
pp. 10771
Author(s):  
Sundararajan Mahalingam ◽  
Srabani Karmakar ◽  
Puttur Santhoshkumar ◽  
Krishna K. Sharma
Keyword(s):  
Deletion Mutant ◽  
Mutant Protein ◽  
Wild Type ◽  
Chaperone Function ◽  
Type Protein ◽  
Wild Type Protein ◽  
Cytotoxicity Studies ◽  
Αb Crystallin ◽  
Apoptotic Activity ◽  
Subunit Organization

Previously, we showed that the removal of the 54–61 residues from αB-crystallin (αBΔ54–61) results in a fifty percent reduction in the oligomeric mass and a ten-fold increase in chaperone-like activity. In this study, we investigated the oligomeric organization changes in the deletion mutant contributing to the increased chaperone activity and evaluated the cytoprotection properties of the mutant protein using ARPE-19 cells. Trypsin digestion studies revealed that additional tryptic cleavage sites become susceptible in the deletion mutant than in the wild-type protein, suggesting a different subunit organization in the oligomer of the mutant protein. Static and dynamic light scattering analyses of chaperone–substrate complexes showed that the deletion mutant has more significant interaction with the substrates than wild-type protein, resulting in increased binding of the unfolding proteins. Cytotoxicity studies carried out with ARPE-19 cells showed an enhancement in anti-apoptotic activity in αBΔ54–61 as compared with the wild-type protein. The improved anti-apoptotic activity of the mutant is also supported by reduced caspase activation and normalization of the apoptotic cascade components level in cells treated with the deletion mutant. Our study suggests that altered oligomeric assembly with increased substrate affinity could be the basis for the enhanced chaperone function of the αBΔ54–61 protein.

scholarly journals Molecular Pathogenesis of Type I Congenital Plasminogen Deficiency: Expression of Recombinant Human Mutant Plasminogens in Mammalian Cells

Blood ◽  
1997 ◽  
Vol 89 (1) ◽  
pp. 183-190 ◽  
Author(s):  
Hiroyuki Azuma ◽  
Nobuaki Mima ◽  
Mitsuo Shirakawa ◽  
Kazumasa Miyamoto ◽  
Hiroshi Yamaguchi ◽  
...  
Keyword(s):  
Sodium Dodecyl ◽  
Resistant Mutant ◽  
Molecular Pathogenesis ◽  
Mutant Protein ◽  
Immunocytochemical Staining ◽  
Type I ◽  
Wild Type ◽  
Transport Pathway ◽  
Stable Transfectants ◽  
Plasminogen Deficiency

We previously reported the genetic abnormality in a Japanese family with type I congenital plasminogen deficiency caused by a Ser572 to Pro572 mutation. To characterize the molecular pathogenesis of the disease in this family, we expressed recombinant human wild-type and mutant (rS572P) plasminogens in COS-1 cells. Activation-resistant wild-type and mutant plasminogen stable transfectants in CHO-K1 cells also were established. Transient transfection and metabolic labeling experiments followed by immunoprecipitation analysis showed that the mutant plasminogen was secreted from COS-1 cells in reduced amounts, compared with the wild type. Endo H digestion of the wild-type and mutant plasminogen showed no shift in their migrations on sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis, indicating that both contain complex type oligosaccharide structures and could therefore be secreted. Furthermore, the secretion of activation-resistant mutant plasminogen was significantly reduced. Pulse-chase experiments and Northern blot analysis showed that the impaired secretion of the mutant plasminogen was the consequence of the accumulation of the mutant protein inside the cells but not of reduced plasminogen mRNA. Immunocytochemical staining of stable transfectants also revealed that CHO-K1 cells expressing the activation-resistant mutant plasminogen stained mainly in the perinuclear area, suggesting delayed processing of the mutant protein in the intracellular transport pathway. We conclude that the impaired secretion of mutant plasminogen, due to intracellular accumulation, is the molecular pathogenesis of type I congenital plasminogen deficiency caused by a Ser572 to Pro572 mutation.

Acetate anion-triggered peroxygenation of non-native substrates by wild-type cytochrome P450s

2015 ◽  
Vol 44 (34) ◽  
pp. 15316-15323 ◽  
Author(s):  
Hiroki Onoda ◽  
Osami Shoji ◽  
Yoshihito Watanabe
Keyword(s):  
Cytochrome P450 ◽  
Cytochrome P450s ◽  
Acetate Anion ◽  
Wild Type ◽  
High Concentration

Wild-type cytochrome P450SPα and cytochrome P450BSβ can catalyze the oxidation of non-native substrates by performing the reaction at a high concentration of the acetate anion.

scholarly journals Dextran sulphate-induced tau assemblies cause endogenous tau aggregation and propagation in wild-type mice

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Masami Masuda-Suzukake ◽  
Genjiro Suzuki ◽  
Masato Hosokawa ◽  
Takashi Nonaka ◽  
Michel Goedert ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Tau Protein ◽  
Guanidine Hydrochloride ◽  
Intracerebral Injection ◽  
Dextran Sulphate ◽  
Wild Type ◽  
Synthetic Filament ◽  
Biochemical Analyses ◽  
Tau Aggregation

Abstract Accumulation of assembled tau protein in the central nervous system is characteristic of Alzheimer’s disease and several other neurodegenerative diseases, called tauopathies. Recent studies have revealed that propagation of assembled tau is key to understanding the pathological mechanisms of these diseases. Mouse models of tau propagation are established by injecting human-derived tau seeds intracerebrally; nevertheless, these have a limitation in terms of regulation of availability. To date, no study has shown that synthetic assembled tau induce tau propagation in non-transgenic mice. Here we confirm that dextran sulphate, a sulphated glycosaminoglycan, induces the assembly of recombinant tau protein into filaments in vitro. As compared to tau filaments induced by heparin, those induced by dextran sulphate showed higher thioflavin T fluorescence and lower resistance to guanidine hydrochloride, which suggests that the two types of filaments have distinct conformational features. Unlike other synthetic filament seeds, intracerebral injection of dextran sulphate-induced assemblies of recombinant tau caused aggregation of endogenous murine tau in wild-type mice. AT8-positive tau was present at the injection site 1 month after injection, from where it spread to anatomically connected regions. Induced tau assemblies were also stained by anti-tau antibodies AT100, AT180, 12E8, PHF1, anti-pS396 and anti-pS422. They were thioflavin- and Gallyas-Braak silver-positive, indicative of amyloid. In biochemical analyses, accumulated sarkosyl-insoluble and hyperphosphorylated tau was observed in the injected mice. In conclusion, we revealed that intracerebral injection of synthetic full-length wild-type tau seeds prepared in the presence of dextran sulphate caused tau propagation in non-transgenic mice. These findings establish that propagation of tau assemblies does not require tau to be either mutant and/or overexpressed.

Galectin-13/placental protein 13: redox-active disulfides as switches for regulating structure, function and cellular distribution

Glycobiology ◽  
2019 ◽  
Vol 30 (2) ◽  
pp. 120-129 ◽  
Author(s):  
Tong Yang ◽  
Yuan Yao ◽  
Xing Wang ◽  
Yuying Li ◽  
Yunlong Si ◽  
...  
Keyword(s):  
Disulfide Bond ◽  
Disulfide Bonds ◽  
Bond Formation ◽  
Gel Filtration ◽  
Wild Type ◽  
High Concentration ◽  
Redox Active ◽  
Placental Protein ◽  
The Relationship ◽  
Low Expression

Abstract Galectin-13 (Gal-13) plays numerous roles in regulating the relationship between maternal and fetal tissues. Low expression levels or mutations of the lectin can result in pre-eclampsia. The previous crystal structure and gel filtration data show that Gal-13 dimerizes via formation of two disulfide bonds formed by Cys136 and Cys138. In the present study, we mutated them to serine (C136S, C138S and C136S/C138S), crystalized the variants and solved their crystal structures. All variants crystallized as monomers. In the C136S structure, Cys138 formed a disulfide bond with Cys19, indicating that Cys19 is important for regulation of reversible disulfide bond formation in this lectin. Hemagglutination assays demonstrated that all variants are inactive at inducing erythrocyte agglutination, even though gel filtration profiles indicate that C136S and C138S could still form dimers, suggesting that these dimers do not exhibit the same activity as wild-type (WT) Gal-13. In HeLa cells, the three variants were found to be distributed the same as with WT Gal-13. However, a Gal-13 variant (delT221) truncated at T221 could not be transported into the nucleus, possibly explaining why women having this variant get pre-eclampsia. Considering the normally high concentration of glutathione in cells, WT Gal-13 should exist mostly as a monomer in cytoplasm, consistent with the monomeric variant C136S/C138S, which has a similar ability to interact with HOXA1 as WT Gal-13.

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