scholarly journals Oligomeric Structural Transition of HspB1 from Chinese Hamster

2021 ◽  
Vol 22 (19) ◽  
pp. 10797
Author(s):  
Nina Kurokawa ◽  
Rio Midorikawa ◽  
Manami Nakamura ◽  
Keiichi Noguchi ◽  
Ken Morishima ◽  
...  
Keyword(s):  
Elevated Temperatures ◽  
Analytical Ultracentrifugation ◽  
Dynamic Equilibrium ◽  
Chinese Hamster ◽  
Molecular Architecture ◽  
Chaperone Function ◽  
Trimeric Complex ◽  
Vital Functions ◽  
Oligomeric Complex ◽  
Almost All

HspB1 is a mammalian sHsp that is ubiquitously expressed in almost all tissues and involved in regulating many vital functions. Although the recent crystal structure of human HspB1 showed that 24 monomers form the oligomeric complex of human HspB1 in a spherical configuration, the molecular architecture of HspB1 is still controversial. In this study, we examined the oligomeric structural change of CgHspB1 by sedimentation velocity analytical ultracentrifugation. At the low temperature of 4 °C, CgHspB1 exists as an 18-mer, probably a trimeric complex of hexamers. It is relatively unstable and partially dissociates into small oligomers, hexamers, and dodecamers. At elevated temperatures, the 24-mer was more stable than the 18-mer. The 24-mer is also in dynamic equilibrium with the dissociated oligomers in the hexameric unit. The hexamer further dissociates to dimers. The disulfide bond between conserved cysteine residues seems to be partly responsible for the stabilization of hexamers. The N-terminal domain is involved in the assembly of dimers and the interaction between hexamers. It is plausible that CgHspB1 expresses a chaperone function in the 24-mer structure.

scholarly journals Like wings of a bird: functional divergence and complementarity between HLA-A and HLA-B molecules

2020 ◽  
Author(s):  
Da Di ◽  
Jose Manuel Nunes ◽  
Wei Jiang ◽  
Alicia Sanchez-Mazas
Keyword(s):  
Balancing Selection ◽  
Functional Divergence ◽  
Peptide Binding ◽  
Human Leukocyte ◽  
Environmental Pressures ◽  
Protein Levels ◽  
Functional Complementarity ◽  
Vital Functions ◽  
Almost All ◽  
Immune Potential

Abstract Human leukocyte antigen (HLA) genes are among the most polymorphic of our genome, as a likely consequence of balancing selection related to their central role in adaptive immunity. HLA-A and HLA-B genes were recently suggested to evolve through a model of joint divergent asymmetric selection conferring all populations, including those with severe loss of diversity, an equivalent immune potential. However, the mechanisms by which these two genes might undergo joint evolution while displaying very distinct allelic profiles in populations worldwide are still unknown. To address this issue, we carried out extensive data analyses (among which factorial correspondence and linear modelling) on 2,909 common and rare HLA-A, HLA-B and HLA-C alleles and 200,000 simulated pathogenic peptides by taking into account sequence variation, predicted peptide-binding affinity and HLA allele frequencies in 123 populations worldwide. Our results show that HLA-A and HLA-B (but not HLA-C) molecules maintain considerable functional divergence in almost all populations, which likely plays an instrumental role in their immune defence. We also provide robust evidence of functional complementarity between HLA-A and HLA-B molecules, which display asymmetric relationships in terms of amino acid diversity at both inter- and intra-protein levels and in terms of promiscuous or fastidious peptide-binding specificities. Like two wings of a flying bird, the functional complementarity of HLA-A and HLA-B is a perfect example, in our genome, of duplicated genes sharing their capacity of assuming common vital functions while being submitted to complex and sometimes distinct environmental pressures.

Structures and ice-binding faces of the alanine-rich type I antifreeze proteinsThis paper is one of a selection of papers published in this special issue entitled “Canadian Society of Biochemistry, Molecular & Cellular Biology 52nd Annual Meeting — Protein Folding: Principles and Diseases” and has undergone the Journal's usual peer review process.

2010 ◽  
Vol 88 (2) ◽  
pp. 223-229 ◽  
Author(s):  
Shruti N. Patel ◽  
Steffen P. Graether
Keyword(s):  
Analytical Ultracentrifugation ◽  
Peer Review Process ◽  
Winter Flounder ◽  
Type I ◽  
Ice Binding ◽  
Shorthorn Sculpin ◽  
High Resolution Structure ◽  
Dimerization Interface ◽  
Α Helix ◽  
Almost All

Antifreeze proteins (AFPs) protect cold-blooded organisms from the damage caused by freezing through their ability to inhibit ice growth. The type I AFP family, found in several fish species, contains proteins that have a high alanine content (>60% of the sequence) and structures that are almost all α-helical. We examine the structure of the type I AFP isoforms HPLC6 from winter flounder, shorthorn sculpin 3, and the winter flounder hyperactive type I AFP. The HPLC6 isoform structure consists of a single α-helix that is 37 residues long, whereas the shorthorn sculpin 3 isoform consists of two helical regions separated by a kink. The high-resolution structure of the hyperactive type I AFP has yet to be determined, but circular dichroism data and analytical ultracentrifugation suggest that the 195 residue protein is a side-by-side dimer of two α-helices. The alanine-rich ice-binding faces of HPLC6 and hyperactive type I AFP are discussed, and we propose that the ice-binding face of the shorthorn sculpin 3 AFP contains Ala14, Ala19, and Ala25. We also propose that the denaturation of hyperactive type I AFP at room temperature is explained by the stabilization of the dimerization interface through hydrogen bonds.

scholarly journals The Use of a Plant-Based Biostimulant Improves Plant Performances and Fruit Quality in Tomato Plants Grown at Elevated Temperatures

Agronomy ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 363 ◽  
Author(s):  
Silvana Francesca ◽  
Carmen Arena ◽  
Bruno Hay Mele ◽  
Carlo Schettini ◽  
Patrizia Ambrosino ◽  
...  
Keyword(s):  
Fruit Quality ◽  
Elevated Temperatures ◽  
Antioxidant Defence ◽  
Tomato Plants ◽  
Growth Physiology ◽  
Yield And Quality ◽  
Antioxidant Defence System ◽  
Negative Impacts ◽  
Substantial Decline ◽  
Almost All

Abiotic stresses can cause a substantial decline in fruit quality due to negative impacts on plant growth, physiology and reproduction. The objective of this study was to verify if the use of a biostimulant based on plant and yeast extracts, rich in amino acids and that contains microelements (boron, zinc and manganese) can ensure good crop yield and quality in tomato plants grown at elevated temperatures (up to 42 °C). We investigated physiological responses of four different tomato landraces that were cultivated under plastic tunnel and treated with the biostimulant CycoFlow. The application of the biostimulant stimulated growth (plants up to 48.5% taller) and number of fruits (up to 105.3%). In plants treated with the biostimulant, antioxidants contents were higher compared to non-treated plants, both in leaves and in fruits. In particular, the content of ascorbic acid increased after treatments with CycoFlow. For almost all the traits studied, the effect of the biostimulant depended on the genotype it was applied on. Altogether, the use of the biostimulant on tomato plants led to better plant performances at elevated temperatures, that could be attributed also to a stronger antioxidant defence system, and to a better fruit nutritional quality.

scholarly journals Interaction of the cellular prion protein with raft-like lipid membranes

2007 ◽  
Vol 388 (1) ◽  
pp. 79-89 ◽  
Author(s):  
Kerstin Elfrink ◽  
Luitgard Nagel-Steger ◽  
Detlev Riesner
Keyword(s):  
Prion Protein ◽  
Lipid Bilayers ◽  
Analytical Ultracentrifugation ◽  
Chinese Hamster ◽  
Lipid Vesicles ◽  
Cellular Prion Protein ◽  
Model Membranes ◽  
Degree Of Saturation ◽  
Insertion Reaction ◽  
Chip Surface

Abstract Conversion of the cellular isoform of the prion protein (PrPC) into the disease-associated isoform (PrPSc) plays a key role in the development of prion diseases. Within its cellular pathway, PrPC undergoes several posttranslational modifications, i.e., the attachment of two N-linked glycans and a glycosyl phosphatidyl inositol (GPI) anchor, by which it is linked to the plasma membrane on the exterior cell surface. To study the interaction of PrPC with model membranes, we purified posttranslationally modified PrPC from transgenic Chinese hamster ovary (CHO) cells. The mono-, di- and oligomeric states of PrPC free in solution were analyzed by analytical ultracentrifugation. The interaction of PrPC with model membranes was studied using both lipid vesicles in solution and lipid bilayers bound to a chip surface. The equilibrium and mechanism of PrPC association with the model membranes were analyzed by surface plasmon resonance. Depending on the degree of saturation of binding sites, the concentration of PrPC released from the membrane into aqueous solution was estimated at between 10-9 and 10-7 M. This corresponds to a free energy of the insertion reaction of -48 kJ/mol. Consequences for the conversion of PrPC to PrPSc are discussed.

Some aspects of lipid biochemistry

1962 ◽  
Vol 156 (964) ◽  
pp. 376-387 ◽  
Keyword(s):  
Dynamic Equilibrium ◽  
Presidential Address ◽  
Living Cells ◽  
British Association ◽  
Lipid Biochemistry ◽  
Chemical Methods ◽  
Single Sentence ◽  
The Bible ◽  
Living Entity ◽  
Almost All

I am at a great disadvantage in comparison to most of the speakers today, for I neither had the good fortune to work in Hopkins’s laboratory, nor did I have the privilege of knowing him. I cannot, therefore, call upon personal recollections of his teaching to link my remarks with his memory. Fortunately the writings of Sir Frederick Gowland Hopkins are to biochemists like the Bible; both provide texts for almost all occasions. I will endeavour to show, with some selected examples, how lipid biochemists have carried forward the general concepts of biochemistry developed by him. There are two recurrent themes in almost all his public addresses, expressed with increasing vigour as years went by. One of these was his emphasis on the necessity of a closer association between chemists and biologists; discarding the sterile mysticism of ‘Vitalism’, Hopkins firmly believed that the life-processes of the cell are catalyzed by intracellular enzymes and obey the laws of chemistry. The second theme was his insistence that the seemingly static composition of any living entity was the result of a dynamic equilibrium of a multitude of reactions. As early as 1913, in his address to the British Association, we find both these themes fully expressed. His thesis was ‘that in the study of the intermediate processes of metabolism we have to deal, not with complex substances which elude ordinary chemical methods, but with simple substances undergoing comprehensible reactions’. In the same lecture he described the life of the cell as ‘the expression of a particular dynamic equilibrium which obtains in a polyphasic system’ (Hopkins 1913). Then in his presidential address to the British Association at Leicester in 1933 the two concepts are expressed in a single sentence, when he defined the essential or ultimate aim of biochemistry as ‘an adequate and acceptable description of molecular dynamics in living cells and tissues’ (Hopkins 1933).

Oligomeric assembly and interactions within the human RuvB-like RuvBL1 and RuvBL2 complexes

2010 ◽  
Vol 429 (1) ◽  
pp. 113-125 ◽  
Author(s):  
Andrew Niewiarowski ◽  
Alison S. Bradley ◽  
Jayesh Gor ◽  
Adam R. McKay ◽  
Stephen J. Perkins ◽  
...  
Keyword(s):  
Molecular Mechanisms ◽  
Structural Model ◽  
Analytical Ultracentrifugation ◽  
Protein Complexes ◽  
Adenine Nucleotides ◽  
Size Exclusion ◽  
Molecular Architecture ◽  
Essential Components ◽  
Exclusion Chromatography

The two closely related eukaryotic AAA+ proteins (ATPases associated with various cellular activities), RuvBL1 (RuvB-like 1) and RuvBL2, are essential components of large multi-protein complexes involved in diverse cellular processes. Although the molecular mechanisms of RuvBL1 and RuvBL2 function remain unknown, oligomerization is likely to be important for their function together or individually, and different oligomeric forms might underpin different functions. Several experimental approaches were used to investigate the molecular architecture of the RuvBL1–RuvBL2 complex and the role of the ATPase-insert domain (domain II) for its assembly and stability. Analytical ultracentrifugation showed that RuvBL1 and RuvBL2 were mainly monomeric and each monomer co-existed with small proportions of dimers, trimers and hexamers. Adenine nucleotides induced hexamerization of RuvBL2, but not RuvBL1. In contrast, the RuvBL1–RuvBL2 complexes contained single- and double-hexamers together with smaller forms. The role of domain II in complex assembly was examined by size-exclusion chromatography using deletion mutants of RuvBL1 and RuvBL2. Significantly, catalytically competent dodecameric RuvBL1–RuvBL2, complexes lacking domain II in one or both proteins could be assembled but the loss of domain II in RuvBL1 destabilized the dodecamer. The composition of the RuvBL1–RuvBL2 complex was analysed by MS. Several species of mixed RuvBL1/2 hexamers with different stoichiometries were seen in the spectra of the RuvBL1–RuvBL2 complex. A number of our results indicate that the architecture of the human RuvBL1–RuvBL2 complex does not fit the recent structural model of the yeast Rvb1–Rvb2 complex.

scholarly journals Asymmetry adjacent to the collagen-like domain in rat liver mannose-binding protein

1997 ◽  
Vol 325 (2) ◽  
pp. 391-400 ◽  
Author(s):  
Russell WALLIS ◽  
Kurt DRICKAMER
Keyword(s):  
Rat Liver ◽  
Analytical Ultracentrifugation ◽  
Binding Protein ◽  
Chinese Hamster Ovary Cells ◽  
Gel Filtration ◽  
Chinese Hamster ◽  
Microbial Pathogens ◽  
Disulphide Bonds ◽  
Mannose Binding Protein ◽  
Mannose Binding

Rat liver mannose-binding protein (MBP-C) is the smallest known member of the collectin family of animal lectins, many of which are involved in defence against microbial pathogens. It consists of an N-terminal collagen-like domain linked to C-terminal carbohydrate-recognition domains. MBP-C, overproduced in Chinese-hamster ovary cells, is post-translationally modified and processed in a manner similar to the native lectin. Analytical ultracentrifugation experiments indicate that MBP-C is trimeric, with a weight-averaged molecular mass of approx. 77 kDa. The rate of sedimentation of MBP-C and its mobility on gel filtration suggest a highly elongated molecule. Anomalous behaviour on gel filtration due to this extended conformation may explain previous suggestions that MBP-C forms a higher oligomer. The polypeptide chains of the MBP-C trimer are linked by disulphide bonds between two cysteine residues at the N-terminal junction of the collagen-like domain. Analysis of an N-terminal tryptic fragment reveals that the disulphide bonding in MBP-C is heterogeneous and asymmetrical. These results indicate that assembly of MBP-C oligomers probably proceeds in a C- to N-terminal direction: trimerization at the C-terminus is followed by assembly of the collagenous domain and finally formation of N-terminal disulphide bonds. The relatively simple organization of MBP-C provides a template for understanding larger, more complex collectins.

The oligomer plasticity of the small heat-shock protein Lo18 from Oenococcus oeni influences its role in both membrane stabilization and protein protection

2012 ◽  
Vol 444 (1) ◽  
pp. 97-104 ◽  
Author(s):  
Magali Maitre ◽  
Stéphanie Weidmann ◽  
Aurélie Rieu ◽  
Daphna Fenel ◽  
Guy Schoehn ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Heat Shock ◽  
Heat Shock Protein ◽  
Analytical Ultracentrifugation ◽  
Quaternary Structure ◽  
Dynamic Equilibrium ◽  
Building Blocks ◽  
Oenococcus Oeni ◽  
Size Exclusion ◽  
Acidic Ph

The ability of the small Hsp (heat-shock protein) Lo18 from Oenococcus oeni to modulate the membrane fluidity of liposomes or to reduce the thermal aggregation of proteins was studied as a function of the pH in the range 5–9. We have determined by size-exclusion chromatography and analytical ultracentrifugation that Lo18 assembles essentially as a 16-mer at acidic pH. Its quaternary structure evolves to a mixture of lower molecular mass oligomers probably in dynamic equilibrium when the pH increases. The best Lo18 activities are observed at pH 7 when the particle distribution contains a major proportion of dodecamers. At basic pH, particles corresponding to a dimer prevail and are thought to be the building blocks leading to oligomerization of Lo18. At acidic pH, the dimers are organized in a double-ring of stacked octamers to form the 16-mer as shown by the low-resolution structure determined by electron microscopy. Experiments performed with a modified protein (A123S) shown to preferentially form dimers confirm these results. The α-crystallin domain of Methanococcus jannaschii Hsp16.5, taken as a model of the Lo18 counterpart, fits with the electron microscopy envelope of Lo18.

scholarly journals Biogenesis of Mitochondrial Metabolite Carriers

Biomolecules ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 1008 ◽  
Author(s):  
Patrick Horten ◽  
Lilia Colina-Tenorio ◽  
Heike Rampelt
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Outer Membrane ◽  
Intermembrane Space ◽  
Inner Membrane ◽  
Chaperone Function ◽  
Mitochondrial Inner Membrane ◽  
Metabolic Reactions ◽  
Almost All ◽  
Related Proteins ◽  
Shed Light

Metabolite carriers of the mitochondrial inner membrane are crucial for cellular physiology since mitochondria contribute essential metabolic reactions and synthesize the majority of the cellular ATP. Like almost all mitochondrial proteins, carriers have to be imported into mitochondria from the cytosol. Carrier precursors utilize a specialized translocation pathway dedicated to the biogenesis of carriers and related proteins, the carrier translocase of the inner membrane (TIM22) pathway. After recognition and import through the mitochondrial outer membrane via the translocase of the outer membrane (TOM) complex, carrier precursors are ushered through the intermembrane space by hexameric TIM chaperones and ultimately integrated into the inner membrane by the TIM22 carrier translocase. Recent advances have shed light on the mechanisms of TOM translocase and TIM chaperone function, uncovered an unexpected versatility of the machineries, and revealed novel components and functional crosstalk of the human TIM22 translocase.

scholarly journals Displacement of One Drug by Another from Carrier or Receptor Sites

1965 ◽  
Vol 58 (11P2) ◽  
pp. 946-955 ◽  
Author(s):  
Bernard B Brodie
Keyword(s):  
Sympathetic Nerve ◽  
Dynamic Equilibrium ◽  
Extracellular Fluid ◽  
Receptor Site ◽  
Biologically Active ◽  
Nerve Endings ◽  
Intrinsic Activity ◽  
Unbound Fraction ◽  
Receptor Sites ◽  
Almost All

The medium of drug transfer is the water of plasma and extracellular fluid. Without complicating factors, the level of drug at a receptor site would be equal to that in the tissues and in plasma, and in dynamic equilibrium. Actually, almost all drugs are reversibly bound to proteins in plasma or tissue. The bound drug, often a high proportion of the total, acts as a reservoir, preventing wild fluctuations between ineffective and toxic levels of the biologically active unbound fraction. Displacement from a receptor site diminishes drug activity, but displacement from plasma or tissue proteins augments the effect by making more unbound drug available at the receptor site. Atropine has no intrinsic activity, but displaces acetylcholine or pilocarpine from receptors at para-sympathetic nerve endings. Similarly guanethidine competes with noradrenaline at sympathetic nerve endings, but in turn is displaced by amphetamine-like drugs. Many acidic drugs (phenylbutazone, sulfonamides, coumarin anticoagulants, salicylates, &c.) are highly bound to one or two sites on albumin molecules. When the limited carrying capacity of the plasma proteins is filled, any unbound surplus is usually soon metabolized or excreted, so the plasma level becomes restabilized. Meanwhile, however, there may be dramatic effects such as hypoglycemia, when sulfonamides are given to patients on tolbutamide, or bleeding when phenylbutazone is given to patients on warfarin. Although hormones, like thyroxine, insulin and cortisol, are carried by specific proteins, they too can be displaced. All the antirheumatic drugs so far examined have displaced cortisol and presumably driven it into tissues. This may be one mechanism of action. Possibly the sulfonylurea drugs act by displacing insulin from proteins in the pancreas, plasma or elsewhere.

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