The molecular chaperone α-crystallin is in kinetic competition with aggregation to stabilize a monomeric molten-globule form of α-lactalbumin

2001 ◽  
Vol 354 (1) ◽  
pp. 79-87 ◽  
Author(s):  
Robyn A. LINDNER ◽  
Teresa M. TREWEEK ◽  
John A. CARVER
Keyword(s):  
Molecular Chaperones ◽  
Molten Globule ◽  
Spectroscopic Techniques ◽  
Essential Requirement ◽  
Substrate Complex ◽  
Low Salt ◽  
Transient Interactions ◽  
Shock Proteins ◽  
Substrate Proteins

In vivo, α-crystallin and other small heat-shock proteins (sHsps) act as molecular chaperones to prevent the precipitation of ‘substrate’ proteins under stress conditions through the formation of a soluble sHsp–substrate complex. Using a range of different salt conditions, the rate and extent of precipitation of reduced α-lactalbumin have been altered. The interaction of α-crystallin with reduced α-lactalbumin under these various salt conditions was then studied using a range of spectroscopic techniques. Under conditions of low salt, α-lactalbumin aggregates but does not precipitate. α-Crystallin is able to prevent this aggregation, initially by stabilization of a monomeric molten-globule species of α-lactalbumin. It is proposed that this stabilization occurs through weak transient interactions between α-crystallin and α-lactalbumin. Eventually a stable, soluble high-molecular-mass complex is formed between the two proteins. Thus it appears that a tendency for α-lactalbumin to aggregate (but not necessarily precipitate) is the essential requirement for α-crystallin–α-lactalbumin interaction. In other words, α-crystallin interacts with a non-aggregated form of the substrate to prevent aggregation. The rate of precipitation of α-lactalbumin is increased significantly in the presence of Na2SO4 compared with NaCl. However, in the former case, α-crystallin is unable to prevent this aggregation and precipitation except in the presence of a large excess of α-crystallin, i.e. at mass ratios more than 10 times greater than in the presence of NaCl. It is concluded that a kinetic competition exists between aggregation and interaction of unfolding proteins with α-crystallin.

Principles of chaperone-mediated protein folding

1995 ◽  
Vol 348 (1323) ◽  
pp. 107-112 ◽  
Keyword(s):  
Protein Folding ◽  
Heat Shock ◽  
Heat Shock Proteins ◽  
Molecular Chaperones ◽  
Cellular Protein ◽  
Chaperone Proteins ◽  
Shock Proteins ◽  
Polypeptide Chains

The recent discovery of molecular chaperones and their functions has changed dramatically our view of the processes underlying the folding of proteins in vivo . Rather than folding spontaneously, most newly synthesized polypeptide chains seem to acquire their native conformations in a reaction mediated by chaperone proteins. Different classes of molecular chaperones, such as the members of the Hsp70 and Hsp60 families of heat-shock proteins, cooperate in a coordinated pathway of cellular protein folding.

scholarly journals The Amyloid Fibril-Forming β-Sheet Regions of Amyloid β and α-Synuclein Preferentially Interact with the Molecular Chaperone 14-3-3ζ

Molecules ◽  
2021 ◽  
Vol 26 (20) ◽  
pp. 6120
Author(s):  
Danielle M. Williams ◽  
David C. Thorn ◽  
Christopher M. Dobson ◽  
Sarah Meehan ◽  
Sophie E. Jackson ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Molecular Chaperones ◽  
Protein Unfolding ◽  
Amyloid Fibrils ◽  
Amyloid Β ◽  
Parkinson’S Diseases ◽  
Amino Acid Form ◽  
Shock Proteins

14-3-3 proteins are abundant, intramolecular proteins that play a pivotal role in cellular signal transduction by interacting with phosphorylated ligands. In addition, they are molecular chaperones that prevent protein unfolding and aggregation under cellular stress conditions in a similar manner to the unrelated small heat-shock proteins. In vivo, amyloid β (Aβ) and α-synuclein (α-syn) form amyloid fibrils in Alzheimer’s and Parkinson’s diseases, respectively, a process that is intimately linked to the diseases’ progression. The 14-3-3ζ isoform potently inhibited in vitro fibril formation of the 40-amino acid form of Aβ (Aβ40) but had little effect on α-syn aggregation. Solution-phase NMR spectroscopy of 15N-labeled Aβ40 and A53T α-syn determined that unlabeled 14-3-3ζ interacted preferentially with hydrophobic regions of Aβ40 (L11-H21 and G29-V40) and α-syn (V3-K10 and V40-K60). In both proteins, these regions adopt β-strands within the core of the amyloid fibrils prepared in vitro as well as those isolated from the inclusions of diseased individuals. The interaction with 14-3-3ζ is transient and occurs at the early stages of the fibrillar aggregation pathway to maintain the native, monomeric, and unfolded structure of Aβ40 and α-syn. The N-terminal regions of α-syn interacting with 14-3-3ζ correspond with those that interact with other molecular chaperones as monitored by in-cell NMR spectroscopy.

scholarly journals Saccharomyces cerevisiaeRot1 Is an Essential Molecular Chaperone in the Endoplasmic Reticulum

2008 ◽  
Vol 19 (8) ◽  
pp. 3514-3525 ◽  
Author(s):  
Masato Takeuchi ◽  
Yukio Kimata ◽  
Kenji Kohno
Keyword(s):  
Molecular Chaperones ◽  
Secretory Pathway ◽  
Temperature Sensitive ◽  
Type I ◽  
Accelerated Degradation ◽  
Transient Interaction ◽  
Protein Functions ◽  
Substrate Proteins

Molecular chaperones prevent aggregation of denatured proteins in vitro and are thought to support folding of diverse proteins in vivo. Chaperones may have some selectivity for their substrate proteins, but knowledge of particular in vivo substrates is still poor. We here show that yeast Rot1, an essential, type-I ER membrane protein functions as a chaperone. Recombinant Rot1 exhibited antiaggregation activity in vitro, which was partly impaired by a temperature-sensitive rot1-2 mutation. In vivo, the rot1-2 mutation caused accelerated degradation of five proteins in the secretory pathway via ER-associated degradation, resulting in a decrease in their cellular levels. Furthermore, we demonstrate a physical and probably transient interaction of Rot1 with four of these proteins. Collectively, these results indicate that Rot1 functions as a chaperone in vivo supporting the folding of those proteins. Their folding also requires BiP, and one of these proteins was simultaneously associated with both Rot1 and BiP, suggesting that they can cooperate to facilitate protein folding. The Rot1-dependent proteins include a soluble, type I and II, and polytopic membrane proteins, and they do not share structural similarities. In addition, their dependency on Rot1 appeared different. We therefore propose that Rot1 is a general chaperone with some substrate specificity.

scholarly journals Hsp70 chaperones are non-equilibrium machines that achieve ultra-affinity by energy consumption

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Paolo De Los Rios ◽  
Alessandro Barducci
Keyword(s):  
Energy Consumption ◽  
Molecular Chaperones ◽  
Atp Hydrolysis ◽  
Fundamental Issue ◽  
Physiological Conditions ◽  
Substrate Complex ◽  
Biochemical Studies ◽  
Shock Proteins ◽  
Non Equilibrium

70-kDa Heat shock proteins are ATP-driven molecular chaperones that perform a myriad of essential cellular tasks. Although structural and biochemical studies have shed some light on their functional mechanism, the fundamental issue of the role of energy consumption, due to ATP-hydrolysis, has remained unaddressed. Here we establish a clear connection between the non-equilibrium nature of Hsp70, due to ATP hydrolysis, and the determining feature of its function, namely its high affinity for its substrates. Energy consumption can indeed decrease the dissociation constant of the chaperone-substrate complex by several orders of magnitude with respect to an equilibrium scenario. We find that the biochemical requirements for observing such ultra-affinity coincide with the physiological conditions in the cell. Our results rationalize several experimental observations and pave the way for further analysis of non-equilibrium effects underlying chaperone functions.

scholarly journals Proteinaceous Transformers: Structural and Functional Variability of Human sHsps

2020 ◽  
Vol 21 (15) ◽  
pp. 5448
Author(s):  
Mareike Riedl ◽  
Annika Strauch ◽  
Dragana A.M. Catici ◽  
Martin Haslbeck
Keyword(s):  
Refractive Index ◽  
Molecular Chaperones ◽  
Active Species ◽  
Chaperone Activity ◽  
Eye Lens ◽  
First Line ◽  
Functional Relationships ◽  
Broad Variety ◽  
Shock Proteins ◽  
Substrate Proteins

The proteostasis network allows organisms to support and regulate the life cycle of proteins. Especially regarding stress, molecular chaperones represent the main players within this network. Small heat shock proteins (sHsps) are a diverse family of ATP-independent molecular chaperones acting as the first line of defense in many stress situations. Thereby, the promiscuous interaction of sHsps with substrate proteins results in complexes from which the substrates can be refolded by ATP-dependent chaperones. Particularly in vertebrates, sHsps are linked to a broad variety of diseases and are needed to maintain the refractive index of the eye lens. A striking key characteristic of sHsps is their existence in ensembles of oligomers with varying numbers of subunits. The respective dynamics of these molecules allow the exchange of subunits and the formation of hetero-oligomers. Additionally, these dynamics are closely linked to the chaperone activity of sHsps. In current models a shift in the equilibrium of the sHsp ensemble allows regulation of the chaperone activity, whereby smaller oligomers are commonly the more active species. Different triggers reversibly change the oligomer equilibrium and regulate the activity of sHsps. However, a finite availability of high-resolution structures of sHsps still limits a detailed mechanistic understanding of their dynamics and the correlating recognition of substrate proteins. Here we summarize recent advances in understanding the structural and functional relationships of human sHsps with a focus on the eye-lens αA- and αB-crystallins.

scholarly journals Synthesis, characterization, and pharmacological evaluation of thiourea derivatives

2020 ◽  
Vol 18 (1) ◽  
pp. 764-777
Author(s):  
Sumaira Naz ◽  
Muhammad Zahoor ◽  
Muhammad Naveed Umar ◽  
Saad Alghamdi ◽  
Muhammad Umar Khayam Sahibzada ◽  
...  
Keyword(s):  
Spectroscopic Techniques ◽  
Organosulfur Compounds ◽  
Bacterial Strains ◽  
Thiourea Derivatives ◽  
Toxicological Effects ◽  
Pharmaceutical Industries ◽  
Uv Visible ◽  
Hematological And Biochemical Parameters

AbstractThioureas and their derivatives are organosulfur compounds having applications in numerous fields such as organic synthesis and pharmaceutical industries. Symmetric thiourea derivatives were synthesized by the reaction of various anilines with CS2. The synthesized compounds were characterized using the UV-visible and nuclear magnetic resonance (NMR) spectroscopic techniques. The compounds were screened for in vitro inhibition of α-amylase, α-glucosidase, acetylcholinesterase (AChE), and butyrylcholinesterase (BuChE) enzymes and for their antibacterial and antioxidant potentials. These compounds were fed to Swiss male albino mice to evaluate their toxicological effects and potential to inhibit glucose-6-phosphatase (G6Pase) inhibition. The antibacterial studies revealed that compound 4 was more active against the selected bacterial strains. Compound 1 was more active against 2,2-diphenyl-1-picrylhydrazyl and 2,2’-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals, AChE, BuChE, and α-glucosidase. Compound 2 was more potent against α-amylase and G6Pase. Toxicity studies showed that compound 4 is safe as it exerted no toxic effect on any of the hematological and biochemical parameters or on liver histology of the experimental animals at any studied dose rate. The synthesized compounds showed promising antibacterial and antioxidant potential and were very active (both in vitro and in vivo) against G6Pase and moderately active against the other selected enzymes used in this study.

Heat shock proteins: Molecular chaperones

1991 ◽  
Vol 19 (4) ◽  
pp. 166-172 ◽  
Author(s):  
Najma Ali ◽  
Naheed Banu
Keyword(s):  
Heat Shock ◽  
Heat Shock Proteins ◽  
Molecular Chaperones ◽  
Shock Proteins

scholarly journals Cross-priming of minor histocompatibility antigen-specific cytotoxic T cells upon immunization with the heat shock protein gp96.

1995 ◽  
Vol 182 (3) ◽  
pp. 885-889 ◽  
Author(s):  
D Arnold ◽  
S Faath ◽  
H Rammensee ◽  
H Schild
Keyword(s):  
Heat Shock ◽  
Heat Shock Proteins ◽  
Heat Shock Protein ◽  
Tumor Cells ◽  
Mhc Class I ◽  
Donor Cell ◽  
Class I ◽  
Heat Shock Protein Gp96 ◽  
Shock Proteins

Vaccination of mice with heat shock proteins isolated from tumor cells induces immunity to subsequent challenge with those tumor cells the heat shock protein was isolated from but not with other tumor cells (Udono, H., and P.K. Srivastava. 1994. J. Immunol. 152:5398-5403). The specificity of this immune response is caused by tumor-derived peptides bound to the heat shock proteins (Udono., H., and P.K. Srivastava. 1993. J. Exp. Med. 178:1391-1396). Our experiments show that a single immunization with the heat shock protein gp96 isolated from beta-galactosidase (beta-gal) expressing P815 cells (of DBA/2 origin) induces cytotoxic T lymphocytes (CTLs) specific for beta-gal, in addition to minor H antigens expressed by these cells. CTLs can be induced in mice that are major histocompatibility complex (MHC) identical to the gp96 donor cells (H-2d) as well as in mice with a different MHC (H-2b). Thus gp96 is able to induce "cross priming" (Matzinger, P., and M.J. Bevan. 1977. Cell. Immunol. 33:92-100), indicating that gp96-associated peptides are not limited to the MHC class I ligands of the gp96 donor cell. Our data confirm the notion that samples of all cellular antigens presentable by MHC class I molecules are represented by peptides associated with gp96 molecules of that cell, even if the fitting MHC molecule is not expressed. In addition, we extend previous reports on the in vivo immunogenicity of peptides associated gp96 molecules to two new groups of antigens, minor H antigens, and proteins expressed in the cytosol.

scholarly journals The Effect of Oxidized Dopamine on the Structure and Molecular Chaperone Function of the Small Heat-Shock Proteins, αB-Crystallin and Hsp27

2021 ◽  
Vol 22 (7) ◽  
pp. 3700
Author(s):  
Junna Hayashi ◽  
Jennifer Ton ◽  
Sparsh Negi ◽  
Daniel E. K. M. Stephens ◽  
Dean L. Pountney ◽  
...  
Keyword(s):  
Heat Shock ◽  
Protein Aggregation ◽  
Molecular Chaperone ◽  
Cross Linking ◽  
Αb Crystallin ◽  
The Cross ◽  
Shock Proteins ◽  
And Function

Oxidation of the neurotransmitter, dopamine (DA), is a pathological hallmark of Parkinson’s disease (PD). Oxidized DA forms adducts with proteins which can alter their functionality. αB-crystallin and Hsp27 are intracellular, small heat-shock molecular chaperone proteins (sHsps) which form the first line of defense to prevent protein aggregation under conditions of cellular stress. In vitro, the effects of oxidized DA on the structure and function of αB-crystallin and Hsp27 were investigated. Oxidized DA promoted the cross-linking of αB-crystallin and Hsp27 to form well-defined dimer, trimer, tetramer, etc., species, as monitored by SDS-PAGE. Lysine residues were involved in the cross-links. The secondary structure of the sHsps was not altered significantly upon cross-linking with oxidized DA but their oligomeric size was increased. When modified with a molar equivalent of DA, sHsp chaperone functionality was largely retained in preventing both amorphous and amyloid fibrillar aggregation, including fibril formation of mutant (A53T) α-synuclein, a protein whose aggregation is associated with autosomal PD. In the main, higher levels of sHsp modification with DA led to a reduction in chaperone effectiveness. In vivo, DA is sequestered into acidic vesicles to prevent its oxidation and, intracellularly, oxidation is minimized by mM levels of the antioxidant, glutathione. In vitro, acidic pH and glutathione prevented the formation of oxidized DA-induced cross-linking of the sHsps. Oxidized DA-modified αB-crystallin and Hsp27 were not cytotoxic. In a cellular context, retention of significant chaperone functionality by mildly oxidized DA-modified sHsps would contribute to proteostasis by preventing protein aggregation (particularly of α-synuclein) that is associated with PD.

In vivo assessment of newly synthesized achiral copper(ii) and zinc(ii) complexes of a benzimidazole derived scaffold as a potential analgesic, antipyretic and anti-inflammatory

RSC Advances ◽  
2016 ◽  
Vol 6 (23) ◽  
pp. 19475-19481 ◽  
Author(s):  
Mohamed F. AlAjmi ◽  
Afzal Hussain ◽  
Ali Alsalme ◽  
Rais Ahmad Khan
Keyword(s):  
Spectroscopic Techniques ◽  
Anti Inflammatory ◽  
In Vivo Assessment

Two new complexes of copper(ii) and zinc(ii) were synthesized and characterized using various spectroscopic techniques. The newly synthesized compounds were screened for analgesic, antipyretic and anti-inflammatory activities.

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